Effectiveness of Positron Emission Tomography/Computed Tomography as a Guide for Palliative Radiation Therapy for Spinal Metastases.

OBJECTIVE: As back pain is the presenting symptom in 95% of patients with epidural spinal metastases, appropriately identifying and treating the most symptomatic levels can provide significant palliation. The purpose of this study was to analyze the ability of combined positron emission tomography (PET)/computed tomography (CT) to identify spinal metastases with high metabolic activity and guide radiotherapy. We sought to correlate improvement in back pain with reduction in standard uptake value (SUV) after treatment. METHODS: Retrospective review was performed of 72 patients with spinal metastases treated with stereotactic ablative radiation therapy at a single center between 2002 and 2014. PET/CT was used to calculate SUVs for spinal metastases, and treatment planning was based on PET/CT results. Preoperative and postoperative pain levels were assessed in all patients. RESULTS: Reduction in pain scores was found in 78% of treated patients. A significant reduction in pain was identified in patients with >5 metastases compared with fewer lesions (P < 0.05). Degree of change in SUV did not correlate significantly with pain relief. However, comparing pretreatment and posttreatment PET/CT, patients with improved pain consistently displayed decreased SUV. CONCLUSIONS: PET/CT was shown to be a useful adjunct in radiation treatment planning with change in SUV correlating with symptomatic improvement. This study paves the way for future prospective studies to further assess utility and cost-effectiveness of this imaging modality in radiation treatment planning for spinal metastases.

Cumulative volumetric analysis as a key criterion for the treatment of brain metastases.

BACKGROUND: Recent studies have demonstrated diminished cognitive function, worse quality of life, and no overall survival benefit from the addition of adjuvant whole brain radiation therapy (WBRT) to stereotactic radiosurgery (SRS) in the management of brain metastases. This study analyzes the treatment outcome of SRS, specifically CyberKnife Radiosurgery, based on the total tumor volume compared to the absolute number of lesions. METHODS: A retrospective analysis of hospital records at Virginia Hospital Center for patients with brain metastases who underwent CyberKnife Radiosurgery between June 2008 and June 2014 was performed. Previous treatment history, metastatic tumor dimensions, and outcomes were recorded. Predictors of neurological defects, local tumor progression, and overall survival were assessed with univariate and multivariate analysis. RESULTS: We identified 130 adult patients with a median age of 61.5years and a median follow-up of 7.1months. Unfavorable outcomes such as death, tumor progression, or neurological defect showed correlation with cumulative tumor volume greater than the median volume of 7cc (p<0.05). Worsening neurological defects showed an association with an increased number of lesions (p<0.02) and age (p<0.05). For local tumor progression, patients who have received WBRT were less likely to progress (.74, 95% CI, .48, 1.10), while those who received chemotherapy (1.48 95% CI, .98, 2.26), or surgery (1.56 95%, CI .98, 2.47) without WBRT were more likely to progress. CONCLUSIONS: Our data suggest that a cumulative tumor volume greater than 7cc correlates with worse outcomes following CyberKnife Radiosurgery. In addition, WBRT appears to have a role in improved survival for patients with increased tumor burden. A prospective study is warranted to validate these findings.

Investigation of gamma knife image registration errors resulting from misalignment between the patient and the imaging axis.

The ability of Leksell GammaPlan to perform stereotactic space localizations with image sets where there is misalignment of the patient's head (stereotactic frame and fiducial apparatus) relative to the computed tomography (CT) scanner coordinate system was studied. Misalignment is sometimes necessary for patient comfort. Results equally apply to magnetic resonance imaging. Seven 0.5 mm diameter CT-visible spheres were rigidly mounted to a string tied tightly at each end to diagonally opposite posts attached to a Leksell stereotactic frame. A standard CT fiducial box was applied to the frame in the usual clinical manner. A baseline CT scan (1 mm slice thickness) was obtained with the fiducial box perfectly aligned with the scanner axis. After localization of the image set, the (x,y,z) coordinate of the center of each sphere was recorded. Repeat CT scans with varying fiducial box misalignments with the imaging axis were subsequently obtained. The mean difference between the base line and the respective coordinates in misaligned geometries was approximately 0.2 mm (sigma=0.2 mm), well within the accuracy of the image sets and the delivery of radiosurgery with the Gamma Knife.

Dosimetric accuracy of a staged radiosurgery treatment.

For large cerebral arteriovenous malformations (AVMs), the efficacy of radiosurgery is limited since the large doses necessary to produce obliteration may increase the risk of radiation necrosis to unacceptable levels. An alternative is to stage the radiosurgery procedure over multiple stages (usually two), effectively irradiating a smaller volume of the AVM nidus with a therapeutic dose during each session. The difference between coordinate systems defined by sequential stereotactic frame placements can be represented by a translation and a rotation. A unique transformation can be determined based on the coordinates of several fiducial markers fixed to the skull and imaged in each stereotactic coordinate system. Using this transformation matrix, isocentre coordinates from the first stage can be displayed in the coordinate system of subsequent stages allowing computation of a combined dose distribution covering the entire AVM. The accuracy of this approach was tested on an anthropomorphic head phantom and was verified dosimetrically. Subtle defects in the phantom were used as control points, and 2 mm diameter steel balls attached to the surface were used as fiducial markers and reference points. CT images (2 mm thick) were acquired. Using a transformation matrix developed with two frame placements, the predicted locations of control and reference points had an average error of 0.6 mm near the fiducial markers and 1.0 mm near the control points. Dose distributions in a staged treatment approach were accurately calculated using the transformation matrix. This approach is simple, fast and accurate. Errors were small and clinically acceptable for Gamma Knife radiosurgery. Accuracy can be improved by reducing the CT slice thickness.

Practical issues in treating heavy patients on a LINAC treatment couch.

Safe delivery of external beam radiation therapy to patients whose weight approaches the tolerance of a treatment couch presents some challenges, particularly if the couch has been in use for several years and has seen significant wear and tear. An analysis of treatment couch design can identify locations that become stressed and could potentially fail when supporting a heavy patient, leading to serious injury. Some practical methods to decrease the likelihood of couch failure are presented in this work. The design and implementation of a lifting apparatus to support the treatment couch is also described.

Sexual, irritative, and voiding outcomes, following stereotactic body radiation therapy for prostate cancer.

BACKGROUND: Urinary symptoms and sexual dysfunction are the two most common complaints following prostate radiotherapy. The impact of hypofractionated treatment on sexual function, irritative symptoms, and voiding symptoms has not been determined within the same patient population. Here we present our institutional data on sexual function, voiding function, irritative symptoms, and treatment response following SBRT. METHODS: This retrospective analysis includes 102 non-metastatic patients treated with SBRT at a single institution between May 2008 and September 2014. The course of radiotherapy consisted of 36.25 Gy (range 35-40) over five daily fractions. International Prostate Symptom Score (IPSS), Sexual Health Inventory for Men (SHIM), and PSA were recorded at baseline, 1, 3, 6, 9, 12, 18, 24, and 36 months after treatment. RESULTS: Median patient age was 72 years old with a median follow-up of 4.3 years. Pretreatment IPSS-I score was 5.21, increasing to 6.97 (p < .001) after 1 month. The mean IPSS-I score returned close to baseline after 3 months to 5.86 and decreased to below baseline after 2 years to 5.09. At 3 months, 9 months, and 2 years, 47.5, 76.2, and 91.1% of patients had reached IPSS-I resolution. The mean IPSS-O score prior to treatment was 5.31 and there was an increase in the score to 6.45 (p = 0.344) at 1 month. The score remained close to baseline and decreased to 4.00 at 2 years and significantly decreased to 3.74 (p = 0.035) at 3 years. 64.4, 82.1, and 96.0% of patients had IPSS-O resolution by 3 months, 9 months, and 2 years. The mean SHIM score prior to treatment was 13.52 and continually decreased to below baseline a year after treatment to 10.56 (p < .001). SHIM score began to improve at 18 months, but was still significantly less than baseline at 12.12 (p = .01). CONCLUSIONS: While an increase in AUA/IPSS score initially occurred, all patients resume normal activities immediately following treatment and the AUA/IPSS symptoms improved from baseline. Irittative symptoms take longer to resolve when compared to obstructive voiding symptoms in patients treated with SBRT. Three year PSA response, reported toxicity, erectile function preservation, and urinary function improvement, shows favorable results.