MR signature matching (MRSIGMA) implementation for true real-time free-breathing volumetric imaging with sub-200 ms latency on an MR-Linac.

PURPOSE: Develop a true real-time implementation of MR signature matching (MRSIGMA) for free-breathing 3D MRI with sub-200 ms latency on the Elekta Unity 1.5T MR-Linac. METHODS: MRSIGMA was implemented on an external computer with a network connection to the MR-Linac. Stack-of-stars with partial kz sampling was used to accelerate data acquisition and ReconSocket was employed for simultaneous data transmission. Movienet network computed the 4D MRI motion dictionary and correlation analysis was used for signature matching. A programmable 4D MRI phantom was utilized to evaluate MRSIGMA with respect to a ground-truth translational motion reference. In vivo validation was performed on patients with pancreatic cancer, where 15 patients were employed to train Movienet and 7 patients to test the real-time implementation of MRSIGMA. Dice coefficients between real-time MRSIGMA and a retrospectively computed 4D reference were used to evaluate motion tracking performance. RESULTS: Motion dictionary was computed in under 5 s. Signature acquisition and matching presented 173 ms latency on the phantom and 193 ms on patients. MRSIGMA presented a mean error of 1.3-1.6 mm for all phantom experiments, which was below the 2 mm acquisition resolution along the motion direction. The Dice coefficient over time between MRSIGMA and reference contours was 0.88 ± 0.02 (GTV), 0.87 ± 0.02(duodenum-stomach), and 0.78 ± 0.02(small bowel), demonstrating high motion tracking performance for both tumor and organs at risk. CONCLUSION: The real-time implementation of MRSIGMA enabled true real-time free-breathing 3D MRI with sub-200 ms imaging latency on a clinical MR-Linac system, which can be used for treatment monitoring, adaptive radiotherapy and dose accumulation mapping in tumors affected by respiratory motion.

Deviation from consensus contouring guidelines predicts inferior local control after spine stereotactic body radiotherapy.

BACKGROUND AND PURPOSE: To analyze the impact of target delineation on local control (LC) after stereotactic body radiotherapy (SBRT) for spine metastasis. MATERIALS AND METHODS: Patients with de novo metastasis of the spine treated with SBRT, excluding those with prostate or hematologic malignancies, were retrospectively reviewed. Deviations from consensus contouring guidelines included incomplete coverage of involved vertebral compartments, omission of adjacent compartments, or unnecessary circumferential coverage. Univariable and multivariable Cox proportional hazard analyses were performed using death as a competing risk. RESULTS: 283 patients with 360 discrete lesions were included with a median follow up of 14.6 months (range 1.2-131.3). The prescription dose was 24-27 Gy in 2-3 fractions for the majority of lesions. Median survival after SBRT was 18.3 months (95 % confidence interval [CI]: 14.8-22.8). The 1 and 2-year local control (LC) rates were 81.1 % (95 % CI: 75.5-85.6 %) and 70.6 % (95 % CI: 63.2-76.8 %), respectively. In total, 60 deviations (16.7 %) from consensus contouring guidelines were identified. Deviation from guidelines was associated with inferior LC (1-year LC 63.0 % vs 85.5 %, p < 0.001). Gastrointestinal primary, epidural extension, and paraspinal extension were all associated with inferior LC on univariable analyses. After adjusting for confounding factors, deviation from guidelines was the strongest predictor of inferior LC (HR 3.52, 95 % CI: 2.11-5.86, p < 0.001). Among guideline-compliant treatments, progressions were mainly in field (61 %) and/or epidural (49 %), while marginal (42 %) and/or epidural progressions (58 %) were most common for those with deviations. CONCLUSIONS: Adherence to consensus contouring guidelines for spine SBRT is associated with superior LC and fewer marginal misses.

Radiomic modeling to predict risk of vertebral compression fracture after stereotactic body radiation therapy for spinal metastases.

OBJECTIVE: In the treatment of spinal metastases with stereotactic body radiation therapy (SBRT), vertebral compression fracture (VCF) is a common and potentially morbid complication. Better methods to identify patients at high risk of radiation-induced VCF are needed to evaluate prophylactic measures. Radiomic features from pretreatment imaging may be employed to more accurately predict VCF. The objective of this study was to develop and evaluate a machine learning model based on clinical characteristics and radiomic features from pretreatment imaging to predict the risk of VCF after SBRT for spinal metastases. METHODS: Vertebral levels C2 through L5 containing metastases treated with SBRT were included if they were naive to prior surgery or radiation therapy, target delineation was based on consensus guidelines, and 1-year follow-up data were available. Clinical features, including characteristics of the patient, disease, and treatment, were obtained from chart review. Radiomic features were extracted from the planning target volume (PTV) on pretreatment CT and T1-weighted MRI. Clinical and radiomic features selected by least absolute shrinkage and selection operator (LASSO) regression were included in random forest classification models, which were trained to predict VCF within 1 year after SBRT. Model performance was assessed with leave-one-out cross-validation. RESULTS: Within 1 year after SBRT, 15 of 95 vertebral levels included in the analysis demonstrated new or progressive VCF. Selected clinical features included BMI, performance status, total prescription dose, dose to 99% of the PTV, lumbar location, and 2 components of the Spine Instability Neoplastic Score (SINS): lytic tumor character and spinal misalignment. Selected radiomic features included 5 features from CT and 3 features from MRI. The best-performing classification model, derived from a combination of selected clinical and radiomic features, demonstrated a sensitivity of 0.844, specificity of 0.800, and area under the receiver operating characteristic (ROC) curve (AUC) of 0.878. This model was significantly more accurate than alternative models derived from only selected clinical features (AUC = 0.795, p = 0.048) or only components of the SINS (AUC = 0.579, p < 0.0001). CONCLUSIONS: In the treatment of spinal metastases with SBRT, a machine learning model incorporating both clinical features and radiomic features from pretreatment imaging predicted VCF at 1 year after SBRT with excellent sensitivity and specificity, outperforming models developed from clinical features or components of the SINS alone. If validated, these findings may allow more judicious selection of patients for prophylactic interventions.

Tumor Control Probability of Radiosurgery and Fractionated Stereotactic Radiosurgery for Brain Metastases.

PURPOSE: As part of the American Association of Physicists in Medicine Working Group on Stereotactic Body Radiotherapy, tumor control probability (TCP) after stereotactic radiosurgery (SRS) and fractionated stereotactic radiosurgery (fSRS) for brain metastases was modeled based on pooled dosimetric and clinical data from published English-language literature. METHODS AND MATERIALS: PubMed-indexed studies published between January 1995 and September 2017 were used to evaluate dosimetric and clinical predictors of TCP after SRS or fSRS for brain metastases. Eligible studies had ≥10 patients and included detailed dose-fractionation data with corresponding ≥1-year local control (LC) data, typically evaluated as a >20% increase in diameter of the targeted lesion using the pre-SRS diameter as a reference. RESULTS: Of 2951 potentially eligible manuscripts, 56 included sufficient dose-volume data for analyses. Accepting that necrosis and pseudoprogression can complicate the assessment of LC, for tumors ≤20 mm, single-fraction doses of 18 and 24 Gy corresponded with >85% and 95% 1-year LC rates, respectively. For tumors 21 to 30 mm, an 18 Gy single-fraction dose was associated with 75% LC. For tumors 31 to 40 mm, a 15 Gy single-fraction dose yielded ∼69% LC. For 3- to 5-fraction fSRS using doses in the range of 27 to 35 Gy, 80% 1-year LC has been achieved for tumors of 21 to 40 mm in diameter. CONCLUSIONS: TCP for SRS and fSRS are presented. For small lesions ≤20 mm, single doses of ≈18 Gy appear generally associated with excellent rates of LC; for melanoma, higher doses seem warranted. For larger lesions >20 mm, local control rates appear to be ≈ 70% to 75% with usual doses of 15 to 18 Gy, and in this setting, fSRS regimens should be considered. Greater consistency in reporting of dosimetric and LC data is needed to facilitate future pooled analyses. As systemic and biologic therapies evolve, updated analyses will be needed to further assess the necessity, efficacy, and toxicity of SRS and fSRS.

A Dose-Response Model of Local Tumor Control Probability After Stereotactic Radiosurgery for Brain Metastases Resection Cavities.

PURPOSE: Recent randomized controlled trials evaluating stereotactic surgery (SRS) for resected brain metastases question the high rates of local control previously reported in retrospective studies. Tumor control probability (TCP) models were developed to quantify the relationship between radiation dose and local control after SRS for resected brain metastases. METHODS AND MATERIALS: Patients with resected brain metastases treated with SRS were evaluated retrospectively. Melanoma, sarcoma, and renal cell carcinoma were considered radio-resistant histologies. The planning target volume (PTV) was the region of enhancement on T1 post-gadolinium magnetic resonance imaging plus a 2-mm uniform margin. The primary outcome was local recurrence, defined as tumor progression within the resection cavity. Cox regression evaluated predictors of local recurrence. Dose-volume histograms for the PTV were obtained from treatment plans and converted to 3-fraction equivalent doses (α/ß = 12 Gy). TCP models evaluated local control at 1-year follow-up as a logistic function of dose-volume histogram data. RESULTS: Among 150 cavities, 41 (27.3%) were radio-resistant. The median PTV volume was 14.6 mL (range, 1.3-65.3). The median prescription was 21 Gy (range, 15-25) in 3 fractions (range, 1-5). Local control rates at 12 and 24 months were 86% and 82%. On Cox regression, larger cavities (PTV > 12 cm3) predicted increased risk of local recurrence (P = .03). TCP modeling demonstrated relationships between improved 1-year local control and higher radiation doses delivered to radio-resistant cavities. Maximum PTV doses of 30, 35, and 40 Gy predicted 78%, 89%, and 94% local control among all radio-resistant cavities, versus 69%, 79%, and 86% among larger radio-resistant cavities. CONCLUSIONS: After SRS for resected brain metastases, larger cavities are at greater risk of local recurrence. TCP models suggests that higher radiation doses may improve local control among cavities of radio-resistant histology. Given maximum tolerated doses established for single-fraction SRS, fractionated regimens may be required to optimize local control in large radio-resistant cavities.

A Prospective Cohort Study of Neural Progenitor Cell-Sparing Radiation Therapy Plus Temozolomide for Newly Diagnosed Patients With Glioblastoma.

BACKGROUND: In treating glioblastoma, irradiation of the neural progenitor cell (NPC) niches is controversial. Lower hippocampal doses may limit neurocognitive toxicity, but higher doses to the subventricular zones (SVZ) may improve survival. OBJECTIVE: To prospectively evaluate the impact of limiting radiation dose to the NPC niches on tumor progression, survival, and cognition in patients with glioblastoma. METHODS: Patients with glioblastoma received resection followed by standard chemoradiation. Radiation dose to the NPC niches, including the bilateral hippocampi and SVZ, was minimized without compromising tumor coverage. The primary outcome was tumor progression in the spared NPC niches. Follow-up magnetic resonance imaging was obtained bimonthly. Neurocognitive testing was performed before treatment and at 6- and 12-mo follow-up. Cox regression evaluated predictors of overall and progression-free survival. Linear regression evaluated predictors of neurocognitive decline. RESULTS: A total of 30 patients enrolled prospectively. The median age was 58 yr. Median mean doses to the hippocampi and SVZ were 49.1 and 41.8 gray (Gy) ipsilaterally, and 16.5 and 19.9 Gy contralaterally. Median times to death and tumor progression were 16.0 and 7.6 mo, and were not significantly different compared to a matched historical control. No patients experienced tumor progression in the spared NPC-containing regions. Overall survival was associated with neurocognitive function (P ≤ .03) but not dose to the NPC niches. Higher doses to the hippocampi and SVZ predicted greater decline in verbal memory (P ≤ .01). CONCLUSION: In treating glioblastoma, limiting dose to the NPC niches may reduce cognitive toxicity while maintaining clinical outcomes. Further studies are needed to confirm these results.

Normal tissue complication probability of vertebral compression fracture after stereotactic body radiotherapy for de novo spine metastasis.

OBJECTIVE: Stereotactic body radiotherapy (SBRT) for spine metastases is associated with post-treatment vertebral compression fracture (VCF). The purpose of this study is to identify clinical and radiation planning characteristics that predict post-SBRT VCF through a novel normal tissue complication probability (NTCP) analysis. METHODS: Patients with de novo spine metastases treated with SBRT between 2009 and 2018 at a single institution were included. Those who had surgical stabilization or radiation to the same site prior to SBRT were excluded. VCF was defined as new development or progression of existing vertebral body height loss not attributable to tumor growth. Probit NTCP models were constructed and fitted using a maximum likelihood approach. A multivariate proportional hazard model was used to estimate time to VCF using the Fine and Gray method. RESULTS: Three hundred and two vertebral segments from 193 patients were treated with a median dose of 24 Gy in 3 fractions (range 15-30 Gy in 1-5 fractions). With a median follow up of 13.9 months, local control was 89.3% at 1 year. A total of 26 SBRT-induced VCFs were observed, with 1 and 2-year cumulative incidences of 4.6% and 6.7%. NTCP modeling demonstrated a steep response of VCF risk to the dose to 80% and 50% volume of the planning target volume (PTV D80% and D50%), but not maximum dose or dose to 1 cc or 10% of PTV. D80% of 25 Gy and D50% of 28 Gy in 3 fractions corresponded to 10% VCF risk. On multivariate analysis, lower body mass index (HR 0.90 per unit increase, p = 0.04), total spinal instability neoplastic score (SINS, HR 2.44 unstable vs stable, p = 0.04), and PTV D80% (HR 1.11 for every Gy increase, p = 0.003) were associated with increased VCF risk. CONCLUSIONS: SBRT provides excellent tumor control for spinal metastases and is associated with low rate of VCF in our cohort. NTCP modeling suggests that the larger volume of spine receiving lower doses are more closely associated with post-SBRT VCF than high dose regions. Under current target delineation methods, common SBRT regimens such as 24 Gy in 2 fractions or 27 Gy in 3 fractions may be inherently associated with VCF risk of 10% or greater. Consensus contouring guidelines should be reevaluated to minimize the volume of irradiated spine in light of these new data.

A Phase 2 Study of Post-Operative Stereotactic Body Radiation Therapy (SBRT) for Solid Tumor Spine Metastases.

PURPOSE: In patients with spinal instability, cord compression, or neurologic deficits, the standard of care is surgery followed by radiation therapy (RT). Recurrence rates after conventional RT remain high. The purpose of this study is to prospectively examine the efficacy of postoperative stereotactic body RT (SBRT) in patients who have undergone surgical intervention for spine metastases. We hypothesize that postoperative SBRT to the spine would be associated with higher local control than historical rates after conventional RT. METHODS AND MATERIALS: Thirty-five adult patients with a Karnofsky Performance Status score ≥40 and spine metastases from solid tumors with no prior overlapping RT and target volumes ≤3 consecutive vertebral levels were enrolled. Thirty-three patients were treated. Two patients underwent treatment to 2 target volumes for a total of 35 target volumes. All patients received SBRT 30 Gy in 5 fractions. Patients were followed with neurological examinations and computed tomography and/or magnetic resonance imaging every 3 months. Neurologic function was assessed at the same time points using the American Spinal Injury Association (ASIA) impairment score. Pain was rated according to the 10-point visual analogue scale and MD Anderson Cancer Center brief pain index. Toxicity was recorded according to National Cancer Institute Common Toxicity Criteria for Adverse Events Version 4. The primary objective was the rate of radiographic local recurrence at 12 months after completion of SBRT. RESULTS: Patient characteristics were as follows: 34.3% had radioresistant primaries; 71.4% were ASIA E and the remainder ASIA D; and the median baseline Karnofsky Performance Status score was 70 (range, 50-100). Radiographic and symptomatic local control at 1 year were 90% (95% confidence interval, 76%-98%). The median time to recurrence in these 3 patients was 3.5 months (range, 3.4-5.8 months), all had radiosensitive tumors, and all recurrences were epidural. No patients experienced wound dehiscence, hardware failure, or spinal cord myelopathy. The median time to return to systemic therapy was 0.5 months (range, 0-9.4 months). CONCLUSIONS: This prospective study of postoperative spine SBRT demonstrates excellent local control with low toxicity. These data suggest superior rates of local control compared with conventional RT; however, a formal comparative study is warranted.

A novel MRI-based score assessing trabecular bone quality to predict vertebral compression fractures in patients with spinal metastasis.

OBJECTIVE: Vertebral compression fractures (VCFs) in patients with spinal metastasis can lead to destabilization and often carry a high risk profile. It is therefore important to have tools that enable providers to predict the occurrence of new VCFs. The most widely used tool for bone quality assessment, dual-energy x-ray absorptiometry (DXA), is not often available at a patient's initial presentation and has limited sensitivity. While the Spinal Instability Neoplastic Score (SINS) has been associated with VCFs, it does not take patients' baseline bone quality into consideration. To address this, the authors sought to develop an MRI-based scoring system to estimate trabecular vertebral bone quality (VBQ) and to assess this system's ability to predict the occurrence of new VCFs in patients with spinal metastasis. METHODS: Cases of adult patients with a diagnosis of spinal metastasis, who had undergone stereotactic body radiation therapy (SBRT) to the spine or neurosurgical intervention at a single institution between 2012 and 2019, were retrospectively reviewed. The novel VBQ score was calculated for each patient by dividing the median signal intensity of the L1-4 vertebral bodies by the signal intensity of cerebrospinal fluid (CSF). Multivariable logistic regression analysis was used to identify associations of demographic, clinical, and radiological data with new VCFs. RESULTS: Among the 105 patients included in this study, 56 patients received a diagnosis of a new VCF and 49 did not. On univariable analysis, the factors associated with new VCFs were smoking status, steroid use longer than 3 months, the SINS, and the novel scoring system-the VBQ score. On multivariable analysis, only the SINS and VBQ score were significant predictors of new VCFs and, when combined, had a predictive accuracy of 89%. CONCLUSIONS: As a measure of bone quality, the novel VBQ score significantly predicted the occurrence of new VCFs in patients with spinal metastases independent of the SINS. This suggests that baseline bone quality is a crucial factor that requires assessment when evaluating these patients' conditions and that the VBQ score is a novel and simple MRI-based measure to accomplish this.

Updated risk models demonstrate low risk of symptomatic radionecrosis following stereotactic radiosurgery for brain metastases.

BACKGROUND: Improvements in systemic therapy continue to increase survival for patients with brain metastases. Updated dosimetric models are required to optimize long-term safety of stereotactic radiosurgery (SRS) for this indication. METHODS: Patients at a single institution receiving SRS from December 2011 to December 2014 were retrospectively reviewed. Patients with radiographic progression of at least one lesion, and with at least 6 months of follow-up from the start of SRS were included. Grade 3 necrosis was defined as requiring surgical intervention. This data were combined with two additional published datasets to construct logistic models describing necrosis risk as a function of dose and volume. RESULTS: From our institution, 294 brain metastases across 57 patients in 139 treatment plans met inclusion criteria. Primary histologies included non-small cell lung cancer (n = 19), melanoma (n = 13), breast carcinoma (n = 9), renal cell carcinoma (n = 7), and other (n = 9). Median follow-up from SRS of first cranial metastasis was 21.7 months (range: 6.3-56.6) and median overall survival was 25.6 months (range: 6.5-56.6). There were eight cases of Grade 1-2 and two cases of Grade 3 necrosis. As a useful clinical reference point, 20 cc of total brain receiving a single-fraction equivalent dose ≥14 Gy corresponded to 12.1% risk for Grade 1-3 (P < 0.003) and 3.4% risk for Grade 3 necrosis (P < 0.001). CONCLUSIONS: These results compare favorably with the QUANTEC brain tolerance estimates for radiosurgery, providing optimism for lower toxicity in the modern era. Additional studies are needed to determine dose tolerance parameters across a broad spectrum of patients.

A prospective evaluation of whole brain volume loss and neurocognitive decline following hippocampal-sparing prophylactic cranial irradiation for limited-stage small-cell lung cancer.

INTRODUCTION: This study evaluated an association between whole brain volume loss and neurocognitive decline following prophylactic cranial irradiation (PCI) for limited-stage small-cell lung cancer (SCLC). METHODS: This was a secondary analysis of a prospective clinical trial that accrued patients at a single institution from 2013 to 2016. Patients with limited-stage SCLC treated with standard chemo-radiation received PCI 25 Gy/10 fractions, with mean hippocampal dose limited to < 8 Gy. Whole brain volumes were measured using MR imaging obtained before and at 6, 12, 18, and 24 months after PCI. Verbal memory was measured by the Hopkins Verbal Learning Test-Revised (HVLT-R) before and at 6 and 12 months after PCI. Univariate and multivariate linear regression evaluated associations between changes in whole brain volume and verbal memory. RESULTS: Twenty-two patients enrolled. The median whole brain volume before PCI was 1301 mL. Subsequent reduction in whole brain volume was greatest at 18 months after PCI (median change - 23 mL, range - 142 to 20, p = 0.03). At 6 months after PCI, reduction in volume was independently associated with decline in verbal memory, measured by two components of the HVLT-R (Delayed Recall: 0.06/mL volume change, p = 0.046; Percent Retained: 0.66/mL volume change, p = 0.030), when controlling for education and global cognitive function at baseline. CONCLUSION: This is the first study to correlate reduction in whole brain volume and decline in neurocognitive function following whole brain radiation therapy (WBRT). This suggests that loss of brain volume after WBRT may be clinically significant and subsequently impact cognition and quality of life.

Characterization and predictive value of volume changes of extremity and pelvis soft tissue sarcomas during radiation therapy prior to definitive wide excision.

PURPOSE: The purpose of this study was to characterize and evaluate the clinical significance of volume changes of soft tissue sarcomas during radiation therapy (RT), prior to definitive surgical resection. MATERIALS AND METHODS: Patients with extremity or pelvis soft tissue sarcomas treated at our institution from 2013 to 2016 with RT prior to resection were identified retrospectively. Tumor volumes were measured using cone-beam computed tomography obtained daily during RT. Linear regression evaluated the linearity of volume changes. Kruskal-Wallis tests, Mann-Whitney U tests, and linear regression evaluated predictors of volume change. Logistic and Cox regression evaluated volume change as a predictor of resection margin status, histologic treatment response, and tumor recurrence. RESULTS: Thirty-three patients were evaluated. Twenty-nine tumors were high grade. Prior to RT, median tumor volume was 189 mL (range, 7.2 to 4,885 mL). Sixteen tumors demonstrated significant linear volume changes during RT. Of these, 5 tumors increased and 11 decreased in volume. Myxoid liposarcoma (n = 5, 15%) predicted decreasing tumor volume (p = 0.0002). Sequential chemoradiation (n = 4, 12%) predicted increasing tumor volume (p = 0.008) and corresponded to longer times from diagnosis to RT (p = 0.01). Resection margins were positive in three cases. Five patients experienced local recurrence, and 7 experienced distant recurrence, at median 8.9 and 6.9 months post-resection, respectively. Volume changes did not predict resection margin status, local recurrence, or distant recurrence. CONCLUSION: Volume changes of pelvis and extremity soft tissue sarcomas followed linear trends during RT. Volume changes reflected histologic subtype and treatment characteristics but did not predict margin status or recurrence after resection.

Extracranial Abscopal Responses after Radiation Therapy for Intracranial Metastases: A Review of the Clinical Literature and Commentary on Mechanism.

The current literature contains a small number of case series and individual case reports that describe radiographic regression of extracranial tumors after treatment of one or more brain metastases with radiation therapy. These observations suggest an abscopal effect that traverses the blood-brain barrier. The purpose of this review is to describe the clinical evidence for this phenomenon and potential mechanistic relationships between radiation, the blood-brain barrier, and the abscopal effect. Among reported cases, the majority of patients received systemic immunotherapy, which is consistent with an immunologic mechanism underlying abscopal responses. Preclinical data suggest that radiation may play multiple roles in this process, including the release of tumor-associated antigens and disruption of the blood-brain barrier. Future studies investigating the abscopal effect would benefit from more rigorous methods to control for patient and treatment factors that may affect distant tumor response.

Neuroimaging and Stereotactic Body Radiation Therapy (SBRT) for Spine Metastasis.

Historically, management options for spinal metastases include surgery for stabilization and decompression and/or external beam radiation therapy (EBRT). EBRT is palliative in nature, as it lacks accurate targeting such that the prescribed radiation doses must be limited in order to maintain safety. Modern advancement in imaging and radiotherapy technology have facilitated the development of stereotactic body radiation therapy (SBRT), which provides increased targeted precision for radiation delivery to tumors resulting in lower overall toxicity, particularly to regional structures such as the spinal cord and esophagus, while delivering higher, more effective, and radically ablative radiation doses.Over the past decade, SBRT has been increasingly utilized as a method of treating spinal metastases either as the primary modality or following surgical intervention in both de novo and reirradiation setting. Numerous studies suggest that SBRT is associated with an 80% to 90% rate of 1-year local control across clinical scenarios. For example, studies of SBRT as the primary treatment modality suggest long-term local control rate of 80% to 95% for spinal metastases. Similarly, SBRT in the adjuvant setting following surgery is associated with local control rates ranging from 70% to 100%. Furthermore, because SBRT allows for lower dose to the spinal cord, it has also been used in patients who have had prior radiation therapy, with studies showing 66% to 93% local control in this scenario.

Local recurrence patterns after postoperative stereotactic radiation surgery to resected brain metastases: A quantitative analysis to guide target delineation.

PURPOSE: In the treatment of resected metastatic brain disease, a recent phase 3 trial by the North Central Cancer Treatment Group (N107C/CEC.3) surprisingly found that the local control rate for whole-brain radiation therapy was better than that of stereotactic radiation surgery (SRS). To optimize target delineation, we performed a quantitative analysis of local failure patterns after postoperative SRS. METHODS AND MATERIALS: Patients with brain metastases who were treated with surgery and SRS to the cavity were evaluated. Local failure was defined by pathologic confirmation or magnetic resonance imaging evidence of progression leading to further overlapping radiation therapy. T1 postgadolinium magnetic resonance imaging scans that were taken preoperatively and at recurrence were co-registered to the simulation computed tomography. Three volumes were compared: (1) Preoperative tumors, (2) resection cavities that were originally contoured as clinical target volumes for SRS, and (3) recurrent tumors. Overlap volume histograms quantified the proximity of the three volumes to the meninges. RESULTS: In the cohort of 173 patients, 18 patients experienced local failure in 19 resection cavities. The original SRS target volume overlapped with a median of 69.6% of the recurrent tumor. When the entire preoperative tumor was included, the overlap with the recurrent tumor increased to a median of 76.8%. Recurrent tumors were closer to the meninges than corresponding preoperative tumors (P = .03) but a median 8.2 mm expansion of the target volume from the meninges was needed to increase overlap with the recurrent tumor to 90%. Increases in overlap with the recurrent tumor were achieved most efficiently by uniformly expanding the contoured cavity and a median 2.8 mm expansion covered 90% of the recurrent tumor. CONCLUSIONS: Our quantitative analysis of recurrence patterns suggests that a larger 3 mm uniform expansion of the SRS target volume substantially increases coverage of the volume that is later occupied by the recurrent tumor and may provide improved local control. The extent of the preoperative tumor in the target volume or expanding the target volume from the meninges provides little benefit.

Predictors of Clinical Outcomes After Hip Arthroscopy: A Prospective Analysis of 1038 Patients With 2-Year Follow-up.

BACKGROUND: As hip arthroscopy has expanded in popularity and volume, more information is needed about indications for the procedure and the predictive factors of clinical outcomes. PURPOSE: To evaluate clinical outcomes of hip arthroscopy in a prospective study and to analyze the cohort to identify factors that are predictive of improvement. STUDY DESIGN: Case-control study; Level of evidence, 3. METHODS: Data were collected prospectively on all patients undergoing hip arthroscopy between February 2008 and June 2012. We included all patients undergoing hip arthroscopy who agreed to participate and who completed 4 patient-reported outcome (PRO) instruments at a minimum 2-year follow-up: the modified Harris Hip Score (mHHS), Nonarthritic Hip Score (NAHS), Hip Outcome Score-Activities of Daily Living (HOS-ADL), and Hip Outcome Score-Sport-Specific Subscale. The NAHS was selected as our primary outcome instrument. All patients with any previous hip conditions were excluded. We analyzed 34 preoperative and intraoperative variables using bivariate and multivariate analyses compared with NAHS. RESULTS: The cohort consisted of 1038 patients with a mean follow-up of 30.1 months (range, 24.0-61.2 months). Mean age was 36.4 years (range, 13.2-76.4 years). All postoperative PRO scores showed significant improvement ( P < .001) at 2 years compared with preoperative scores. Bivariate analysis identified 15 variables (7 categorical and 8 continuous) and multivariate analysis identified 10 variables that were predictive of 2-year postoperative NAHS. Preoperative NAHS, preoperative HOS-ADL, preoperative mHHS, age, duration of symptoms, body mass index (BMI), and revision hip arthroscopy were identified as predictive factors in both bivariate and multivariate analyses. The predictive value of preoperative NAHS was accentuated for patients with higher BMI. CONCLUSION: This study reports favorable clinical outcomes in the largest cohort of hip arthroscopies with a minimum 2-year follow-up in the literature to date. Factors identified as predictive in both bivariate and multivariate analyses included preoperative NAHS, HOS-ADL, and mHHS; age; duration of symptoms; BMI; and revision hip arthroscopy. These predictive factors may be useful to the clinician in determining prognosis and operative indications for hip arthroscopy.

Clinical outcomes of patients with symptomatic acetabular rim fractures after arthroscopic FAI treatment.

This study aims to investigate the influence of the acetabular rim fractures on outcomes of hip arthroscopy at minimum 2-year follow-up. Between January 2009 and August 2012, data were prospectively collected on all patients undergoing hip arthroscopy. Anatomic findings, including presence of rim fractures, were recorded intraoperatively. Patients were assessed preoperatively and at 3 months, 1 year and minimum 2 years postoperatively with four patient-reported outcome measures: modified Harris Hip Score, Non-Arthritic Hip Score, Hip Outcome Score-Activities of Daily Living and Hip Outcome Score-Sport Specific Subscales. Pain was estimated using a visual analog scale. Satisfaction was measured on a scale from 0 to 10. Patients with rim fractures were identified and retrospectively matched to a control group based on gender, BMI category, and age at surgery within 3 years and compared in terms of demographic factors, intraoperative findings, procedures and outcomes. Twenty-one patients with rim fractures were matched to a control group of 21 patients with symptomatic femoroacetabular impingement without rim fractures. No significant differences were detected with respect to demographic characteristics, surgical procedures (besides the removal of rim fractures), or in terms of preoperative, postoperative, or improvement in patient-reported outcome scores and satisfaction. The presence or absence of an acetabular rim fracture does not significantly influence clinical outcomes at minimum 2-year follow-up after hip arthroscopy. Case-control study design is used in this study.

Central Acetabular Impingement Is Associated With Femoral Head and Ligamentum Teres Damage: A Cross-Sectional Matched-Pair Analysis of Patients Undergoing Hip Arthroscopy for Acetabular Labral Tears.

PURPOSE: The primary purpose of this study was to report the prevalence of femoral head articular damage in patients with a central acetabular osteophyte (CAO) that was identified during hip arthroscopy and compare it with that in a matched control group without a CAO. A secondary purpose was to identify rates of coexisting intra-articular pathology in both patient groups. METHODS: Intraoperative data were collected prospectively on all hip arthroscopy patients at our institution between 2008 and 2015. The inclusion criteria for this study were CAOs identified during hip arthroscopy for a labral tear and/or femoroacetabular impingement. The exclusion criteria were Tönnis grade greater than 0, previous hip conditions, and prior surgical interventions. The matched control group was selected based on sex, age ± 5 years, body mass index, and Workers' Compensation claim at a 3:1 ratio and comprised patients who underwent hip arthroscopy for a labral tear and/or femoroacetabular impingement without a CAO. The size and location of labral tears and chondral lesions were recorded in square millimeters with a 5-mm probe and by the clock-face method. RESULTS: The CAO group consisted of 126 patients, who were matched to 378 patients in the control group. Femoral and acetabular chondral damage grades were significantly different between the 2 groups (P < .001). Of patients with CAOs, 55% had femoral head chondral damage compared with 24% of the control patients. The mean size of femoral chondral damage was 3.2 cm2 in the CAO group and 1.7 cm2 in the control group. The mean size of acetabular chondral damage was 1.7 cm2 in the CAO group and 1.2 cm2 in the control group. Both femoral and acetabular chondral damage sizes were significantly larger in the CAO group (P ≤ .007). The prevalence of ligamentum teres tears was significantly different between the 2 groups (P < .001). There were no statistically significant differences in the types of labral tears between the 2 groups (P = .625). CONCLUSIONS: This study showed that patients with CAOs had a significantly higher prevalence of femoral chondral damage and ligamentum teres tears than matched controls. LEVEL OF EVIDENCE: Level III, comparative study.

Relationship Between Age at Onset of Symptoms and Intraoperative Findings in Hip Arthroscopic Surgery.

BACKGROUND: Hip arthroscopic surgery is intended to treat multiple abnormalities in an effort to delay the progression to osteoarthritis, especially in young patients. However, the length of time in which patients experience joint pain before seeking a specialist for a diagnosis can delay hip preservation surgery and influence clinical outcomes. PURPOSE: To investigate the relationship between age at symptom onset and findings during hip arthroscopic surgery as well as outcomes after 2 years of clinical follow-up. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: From February 2008 to March 2015, data were prospectively collected on all patients undergoing hip arthroscopic surgery at a single institution. Anatomic and pathological characteristics were recorded intraoperatively. The mean age at onset of symptoms was calculated and correlated with intraoperative findings using Pearson correlation and logistic regression. All patients were assessed preoperatively and postoperatively with 4 patient-reported outcome measures: the modified Harris Hip Score (mHHS), the Non-Arthritic Hip Score (NAHS), the Hip Outcome Score-Activities of Daily Living (HOS-ADL), and the Hip Outcome Score-Sport-Specific Subscale (HOS-SSS). Pain was estimated using a visual analog scale (VAS). Furthermore, patients with an age at onset of symptoms below the mean (34.6 years) were compared with those of an age at onset of symptoms above the mean. The 2 groups were compared using the Student t test and the chi-square test. P values <.05 were considered significant. RESULTS: A total of 1697 patients met the inclusion criteria. Body mass index was weakly correlated with age (r = 0.3). Younger patients had a lower prevalence of combined Seldes type 1 and 2 labral tears; acetabular labrum articular disruption (ALAD) grade 2, 3, and 4 acetabular chondral lesions; and Outerbridge grade 2, 3, and 4 femoral head chondral lesions (P < .05 for all). More advanced age was correlated with wider labral tears and chondral lesions based on a clock face (r ≥ 0.2, P < .05). Patients younger than 34.6 years had a lower prevalence of gluteus medius and ligamentum teres tears (P ≤ .001). The prevalence of synovitis was positively correlated with age, while instability was negatively correlated with age (P = .04). The improvement of scores from preoperatively to 2-year follow-up in the younger patient group was 62.69 to 83.82 for the mHHS, 64.97 to 87.35 for the HOS-ADL, 43.46 to 73.37 for the HOS-SSS, 63.01 to 85.19 for the NAHS, and 5.61 to 2.53 for pain VAS. All score improvements were statistically significant (P < .001). Regarding the older patient group, the improvement of scores from preoperatively to 2-year follow-up was 58.55 to 78.27 for the mHHS, 57.59 to 79.66 for the HOS-ADL, 35.63 to 61.88 for the HOS-SSS, 55.28 to 77.55 for the NAHS, and 5.72 to 3.01 for pain VAS. All score improvements were statistically significant (P < .001). CONCLUSION: Of the multiple intraoperative findings in hip arthroscopic surgery, many are related to age at onset of symptoms. Although we found a statistically significant improvement in clinical outcomes in both groups after 2-year follow-up, apparently the less complex and smaller lesions observed in both the articular cartilage and the labrum of younger patients result in better outcomes compared with older patients.

Correlation Between Changes in Visual Analog Scale and Patient-Reported Outcome Scores and Patient Satisfaction After Hip Arthroscopic Surgery.

BACKGROUND: Improvements in pain, function, and patient satisfaction are used to evaluate the outcomes of hip arthroscopic surgery. PURPOSE: To identify correlations between the visual analog scale (VAS) score for pain and patient satisfaction with 4 commonly used patient-reported outcome (PRO) scores to determine to what extent changes in these 2 parameters are reflected in each of the PRO scores. STUDY DESIGN: Cohort study (diagnosis); Level of evidence, 3. METHODS: Patients undergoing hip arthroscopic surgery between February 2008 and February 2013 were assessed prospectively before surgery, at 3 months, and annually thereafter with the modified Harris Hip Score (mHHS), Nonarthritic Hip Score (NAHS), Hip Outcome Score-sports-specific subscale (HOS-SSS), and Hip Outcome Score-activities of daily living (HOS-ADL). Patients were also assessed using a 10-point VAS for pain and queried for satisfaction at the same time points ("0" indicated no pain, and "10" indicated complete satisfaction with surgery). The VAS score and patient satisfaction were correlated with changes in the 4 PRO scores. RESULTS: During the study period, 1417 patients underwent hip arthroscopic surgery, of whom 1137 patients had 2-year postoperative PRO scores after primary surgery. There was a significant improvement in all PRO scores at 2-year follow-up. The mean improvements in mHHS, NAHS, HOS-ADL, and HOS-SSS scores were 16.7, 21.6, 19.7, and 22.7 points, respectively. The mean improvement in the VAS score was 2.9 points. Mean patient satisfaction at 2-year follow-up was 7.74 (of 10). There was a statistically significant correlation between the VAS and patient satisfaction scores and changes in each of the 4 PRO scores. The strength of the correlation was moderate. CONCLUSION: This study demonstrated a moderate correlation between the VAS and patient satisfaction outcomes and changes in 4 commonly used PRO scores in hip arthroscopic surgery (mHHS, HOS-ADL, HOS-SSS, and NAHS). In addition to several PRO instruments, a VAS for pain and patient satisfaction may add to the overall assessment of the efficacy of hip arthroscopic surgery.