Radiotherapy for Atypical Teratoid/Rhabdoid Tumor (ATRT) on the Pediatric Proton/Photon Consortium Registry (PPCR).

PURPOSE: Atypical teratoid/rhabdoid tumors (ATRT) of the central nervous system (CNS) are rare tumors with a poor prognosis and variable use of either focal or craniospinal (CSI) radiotherapy (RT). Outcomes on the prospective Pediatric Proton/Photon Consortium Registry (PPCR) were evaluated according to RT delivered. METHODS: Pediatric patients receiving RT were prospectively enrolled on PPCR to collect initial patient, disease, and treatment factors as well as provide follow-up for patient outcomes. All ATRT patients with evaluable data were included. Kaplan-Meier analyses with log-rank p-values and cox proportional hazards regression were performed. RESULTS: The PPCR ATRT cohort includes 68 evaluable ATRT patients (median age 2.6 years, range 0.71-15.40) from 2012 to 2021. Median follow-up was 40.8 months (range 3.4-107.7). Treatment included surgery (65% initial gross total resection or GTR), chemotherapy (60% with myeloablative therapy including stem cell rescue) and RT. For patients with M0 stage (n = 60), 50 (83%) had focal RT and 10 (17%) had CSI. Among patients with M + stage (n = 8), 3 had focal RT and 5 had CSI. Four-year overall survival (OS, n = 68) was 56% with no differences observed between M0 and M + stage patients (p = 0.848). Local Control (LC) at 4 years did not show a difference for lower primary dose (50-53.9 Gy) compared to ≥ 54 Gy (73.3% vs 74.7%, p = 0.83). For patients with M0 disease, four-year OS for focal RT was 54.6% and for CSI was 60% (Hazard Ratio 1.04, p = 0.95. Four-year event free survival (EFS) among M0 patients for focal RT was 45.6% and for CSI was 60% (Hazard Ratio 0.71, p = 0.519). For all patients, the 4-year OS comparing focal RT with CSI was 54.4% vs 60% respectively (p = 0.944), and the 4-year EFS for focal RT or CSI was 42.8% vs 51.4% respectively (p = 0.610). CONCLUSION: The PPCR ATRT cohort found no differences in outcomes according to receipt of either higher primary dose or larger RT field (CSI). However, most patients were M0 and received focal RT. A lower primary dose (50.4 Gy), regardless of patient age, is appealing for further study as part of multi-modality therapy.

Variation in Proton Craniospinal Irradiation Practice Patterns in the United States: A Pediatric Proton Consortium Registry (PPCR) Study.

PURPOSE: Craniospinal irradiation (CSI) is commonly used for pediatric brain tumors with a propensity for spread in craniospinal fluid, principally medulloblastoma. Evolving technology has led to the use of highly conformal radiation therapy (RT) techniques for CSI, including proton therapy. Target delineation and plan coverage are critical for CSI, but there is ongoing controversy and variability in these realms, with little available data on practice patterns. We sought to characterize proton CSI practice patterns in the United States by examining CSI plans in the Pediatric Proton/Photon Consortium Registry (PPCR). MATERIALS AND METHODS: PPCR was queried for data on proton CSI patients from 2015 to early 2020. Each plan was manually reviewed, determining patient position; prescription dose; and coverage of optic nerves, vertebral bodies, spinal nerve roots, sacral nerves, and cranial foramina, among other variables. Two radiation oncologists blinded to clinical data and treating institution assessed coverage at the 95% prescription isodose line and per published European Society for Paediatric Oncology guidelines. Variability in coverage was assessed with nonparametric tests and univariate and multivariate logistic regression. RESULTS: PPCR supplied data for 450 patients, 384 of whom had an evaluable portion of a CSI plan. Most patients (90.3%) were supine. Optic nerves were fully covered in 48.2%; sacral nerves in 87.7%; cranial foramina in 69.3%; and spinal nerves in 95.6%. Vertebral body (VB) sparing was used in 18.6% of skeletally immature cases, increasing over time (P < .001). Coverage in all categories was significantly different among treating institutions, on univariate and multivariate analyses. Cribriform plate deficits were rare, with marginal misses of the foramen ovale (17.4%) and frontal lobe (12%) most common. CONCLUSION: We found consistent variation based on treating institution in proton CSI practices including optic nerve, VB, sacral nerve, cranial, and spinal nerve coverage. These data may serve as a baseline quantification of current proton CSI practices in the United States as they continue to evolve.

Factors Associated With Acute Toxicity in Pediatric Patients Treated With Proton Radiation Therapy: A Report From the Pediatric Proton Consortium Registry.

PURPOSE: Limited prospective information regarding acute toxicity in pediatric patients receiving proton therapy (PT) exists. In this study, Pediatric Proton Consortium Registry (PPCR) data was analyzed for factors associated with development of acute toxicity in children receiving passively scattered or pencil beam scanning PT. METHODS AND MATERIALS: Pediatric patients treated with PT and enrolled on the PPCR from 2016 to 2017 at 7 institutions were included. Data were entered on presence versus absence of acute general, cardiac, endocrine, eye, gastrointestinal, genitourinary, hematologic, mouth, musculoskeletal, neurologic, psychological, respiratory, and skin toxicities before (baseline) and at the end of PT (acute). Associations between patient and treatment variables with development of acute toxicity were assessed with multivariable modeling. RESULTS: Of 422 patients included, PT technique was passively scattered in 241 (57%), pencil beam scanning in 180 (43%), and missing in 1 (<1%) patient. Median age was 9.9 years. Daily anesthesia for treatment was used in 169 (40%). Treatments were categorized as craniospinal irradiation (CSI; n = 100, 24%), focal central nervous system PT (n = 157, 38%), or body PT (n = 158, 38%). Passively scattered PT was associated with increased risk of hematologic toxicity compared with pencil beam scanning PT (odds ratio [OR]: 3.03; 95% confidence interval [CI], 1.38-6.70; P = .006). There were no other differences toxicities between PT techniques. Uninsured patients had increased risk of GI (OR: 2.71; 95% CI, 1.12-6.58; P = .027) and hematologic toxicity (OR: 10.67; 95% CI, 2.68-42.46; P <.001). Patients receiving concurrent chemotherapy were more likely to experience skin (OR: 2.45; 95% CI, 1.23-4.88; P = .011), hematologic (OR: 2.87; 95% CI, 1.31-6.25; P = .008), GI (OR: 2.37; 95% CI, 1.33-4.21; P = .003), and mouth toxicities (OR: 2.03; 95% CI, 1.10-3.73; P = .024). Patients receiving 49 to 55 Gy were more likely to experience skin (OR: 2.18; 95% CI, 1.06-4.44; P = .033) toxicity than those receiving <49 Gy. CONCLUSIONS: The PPCR registry highlights broad differences in acute toxicity rates in children receiving PT, and identifies opportunities for improvements in prevention, monitoring, and treatment of toxicities.

Proton pencil beam scanning treatment with feedback based voluntary moderate breath hold.

Introduction The aim of this article is to introduce a novel protocol for proton pencil beam scanning treatment with moderate deep inspiration breath hold (mDIBH) and report on our clinical implementation results. Methods Three computed tomography (CT) scannings to build the patient's anatomy model were performed during the patient's voluntary mDIBH. All 3 CT scans were used in the optimization during the treatment planning process. Both orthogonal kV imaging and cone-beam computed tomography (CBCT) were implemented for patient alignment with BH prior to the treatment. The BH CBCT images were analyzed for BH reproducibility and the virtual total dose (VTD) retrospectively. To find the VTD, a series of deformable image registrations (DIR) were performed between CBCT and pCT. The effect of the variation of lung density on the dose distribution was also analyzed in the study. Results The values of the mean, standard deviation, maximum, and minimum of the tumor location difference between the CBCT and pCT were 1.9, 1.6, 4.7, and 0.0 mm, respectively. The percentage difference in D99% of CTVs between VTD and the nominal plan was within 1.5%. Conclusions The feedback-based voluntary moderate BH proton PBS treatment was successfully performed in our clinic. This study shows that there is a potential to implement the BH treatment widely in proton centers.

An open invitation to join the Pediatric Proton/Photon Consortium Registry to standardize data collection in pediatric radiation oncology.

OBJECTIVE: The Pediatric Proton/Photon Consortium Registry (PPCR) is a comprehensive data registry composed of pediatric patients treated with radiation. It was established to expedite outcomes-based research. The attributes which allow the PPCR to be a successful collaboration are reviewed. METHODS AND MATERIALS: Current eligibility criteria are radiotherapy patients < 22 years treated at one of the 15 US participating institutions. Detailed health and treatment data are collected about the disease presentation and treatment exposures, and annually thereafter, in REDCap (Research Electronic Data Capture). DICOM (Digital Imaging and Communications in Medicine) imaging and radiation plans are collected through MIM/MIMcloud. An optional patient-reported quality-of-life (PedsQL) study is administered at 10 sites. RESULTS: Accrual started October 2012 with 2,775 participants enrolled as of 25 July 2019. Most patients, 62.0%, were treated for central nervous system (CNS) tumors, the most common of which are medulloblastoma (n = 349), ependymoma (n = 309), and glial/astrocytoma tumors (n = 279). The most common non-CNS diagnoses are rhabdomyosarcoma (n = 284), Ewing's sarcoma (n = 153), and neuroblastoma (n = 130). While the majority of participants are US residents, 18.7% come from 36 other countries. Over 685 patients participate in the PedsQL study. CONCLUSIONS: The PPCR is a valuable research platform capable of answering countless research questions that will ultimately improve patient care. Centers outside of the USA are invited to participate directly or may engage with the PPCR to align data collection strategies to facilitate large-scale international research. ADVANCES IN KNOWLEDGE: For investigators looking to carry out research in a large pediatric oncology cohort or interested in registry work, this paper provides an updated overview of the PPCR.

Patterns of proton therapy use in pediatric cancer management in 2016: An international survey.

PURPOSE: To facilitate the initiation of observational studies on late effects of proton therapy in pediatric patients, we report on current patterns of proton therapy use worldwide in patients aged less than 22 years. MATERIALS & METHODS: Fifty-four proton centers treating pediatric patients in 2016 in 11 countries were invited to respond to a survey about the number of patients treated during that year by age group, intent of treatment, delivery technique and tumor types. RESULTS: Among the 40 participating centers (participation rate: 74%), a total of 1,860 patients were treated in 2016 (North America: 1205, Europe: 432, Asia: 223). The numbers of patients per center ranged from 1 to 206 (median: 29). Twenty-four percent of the patients were <5 years of age, and 50% <10 years. More than 30 pediatric tumor types were identified, mainly treated with curative intent: 48% were CNS, 25% extra-cranial sarcomas, 7% neuroblastoma, and 5% hematopoietic tumors. About half of the patients were treated with pencil beam scanning. Treatment patterns were broadly similar across the three continents. CONCLUSION: To our knowledge, this survey provides the first worldwide assessment of proton therapy use for pediatric cancer management. Since previous estimates in the United States and Europe, CNS tumors remain the cancer types most commonly treated with protons in 2016. However, the proportion of extra-cranial tumors is growing worldwide. The typically low numbers of patients treated in each center indicate the need for international research collaborations to assess long-term outcomes of proton therapy in pediatric patients.

An Update From the Pediatric Proton Consortium Registry.

BACKGROUND/OBJECTIVES: The Pediatric Proton Consortium Registry (PPCR) was established to expedite proton outcomes research in the pediatric population requiring radiotherapy. Here, we introduce the PPCR as a resource to the oncology community and provide an overview of the data available for further study and collaboration. DESIGN/METHODS: A multi-institutional registry of integrated clinical, dosimetric, radiographic, and patient-reported data for patients undergoing proton radiation therapy was conceived in May 2010. Massachusetts General Hospital began enrollment in July of 2012. Subsequently, 12 other institutions joined the PPCR and activated patient accrual, with the latest joining in 2017. An optional patient-reported quality of life (QoL) survey is currently implemented at six institutions. Baseline health status, symptoms, medications, neurocognitive status, audiogram findings, and neuroendocrine testing are collected. Treatment details of surgery, chemotherapy, and radiation therapy are documented and radiation plans are archived. Follow-up is collected annually. Data were analyzed 25 September, 2017. RESULTS: A total of 1,854 patients have consented and enrolled in the PPCR from October 2012 until September 2017. The cohort is 55% male, 70% Caucasian, and comprised of 79% United States residents. Central nervous system (CNS) tumors comprise 61% of the cohort. The most common CNS histologies are as follows: medulloblastoma (n = 276), ependymoma (n = 214), glioma/astrocytoma (n = 195), craniopharyngioma (n = 153), and germ cell tumors (n = 108). The most common non-CNS tumors diagnoses are as follows: rhabdomyosarcoma (n = 191), Ewing sarcoma (n = 105), Hodgkin lymphoma (n = 66), and neuroblastoma (n = 55). The median follow-up is 1.5 years with a range of 0.14 to 4.6 years. CONCLUSION: A large prospective population of children irradiated with proton therapy has reached a critical milestone to facilitate long-awaited clinical outcomes research in the modern era. This is an important resource for investigators both in the consortium and for those who wish to access the data for academic research pursuits.

Ototoxicity and cochlear sparing in children with medulloblastoma: Proton vs. photon radiotherapy.

PURPOSE: To compare ototoxicity rates between medulloblastoma patients treated with protons vs. photons. MATERIALS AND METHODS: The study included 84 children diagnosed with medulloblastoma treated with either passively scattered protons (n = 38) or photons (n = 46). Patients underwent maximal safe resection followed by craniospinal irradiation, posterior fossa and/or tumor bed boost and chemotherapy according to one of 3 multi-institutional trials. Median audiogram follow-up was 56 months for protons and 66 months for photons. RESULTS: Mean cochlear dose (Dmc) was lower in patients treated with protons for both standard (p < 0.0001) and high-risk disease (p < 0.001). Grade 3 and 4 ototoxicity was seen in 7 of 75 (9.3%) and 9 of 91 (9.9%) ears (Brock, p = 0.91), 13 of 75 (17.3%) and 19 of 91 (20.9%) ears (POG, p = 0.56), and 15 of 75 (20.0%) and 21 of 91 (23.1%) ears (SIOP Boston, p = 0.63) with protons and photons respectively. CONCLUSIONS: While cochlear doses were lower in the proton group, patients treated with either protons or photons had similar Grade 3 and 4 ototoxicity rates.

Diagnostic Performance of Ultrasonography for Pediatric Appendicitis: A Night and Day Difference?

RATIONALE AND OBJECTIVES: For imaging pediatric appendicitis, ultrasonography (US) is preferred because of its lack of ionizing radiation, but is limited by operator dependence. This study investigates the US diagnostic performance during night shifts covered by radiology trainees compared to day shifts covered by attending radiologists. MATERIALS AND METHODS: Appy-Scores (1 = completely visualized normal appendix; 2 = partially visualized normal appendix; 3 = nonvisualized appendix with no inflammatory changes in the expected region of the appendix; 4 = equivocal; 5a = nonperforated appendicitis; 5b = perforated appendicitis) from 2935 US examinations (2161:774, day-to-night) from July 2013 to 2014 were correlated with the intraoperative diagnoses and the clinical follow-up. The diagnostic performance of trainees and attendings was compared with Fisher exact test. Interobserver agreement was measured by Cohen kappa coefficient. RESULTS: Appendicitis prevalence was 25.3% (day) and 22.5% (night). Sensitivity, specificity, accuracy, negative predictive value, and positive predictive vale were 94.0%, 93.7%, 93.8%, 97.9%, and 83.4% during the day and 92.0%, 91.2%, 91.3%, 97.5%, and 75.2% at night. Specificity (P = .048) and positive predictive value (P = .011) differed, with more false positives at night (7%) than during the day (4.7%). Trainee and attending agreement was high (k = 0.995), with Appy-Scores of 1, 4, and 5a most frequently discordant. CONCLUSIONS: US has a high diagnostic performance and interobserver agreement for pediatric appendicitis when interpreted by radiology trainees during night shifts or attending radiologists during day shifts. However, lower specificity and positive predictive value at night warrants a thorough trainee education to avoid false-positive examinations.

Predictors and Patterns of Regional Recurrence Following Lung SBRT: A Report From the Elekta Lung Research Group.

INTRODUCTION: The objective of this study was to determine the predictors and patterns of regional recurrence (RR) following stereotactic body radiotherapy (SBRT) for primary lung cancers. MATERIAL AND METHODS: Details of patient factors, treatment, and outcome factors were extracted from a multi-institutional (5) database. All events were calculated from the end of radiotherapy. Estimates of local recurrence, RR, and distant metastases (DM) were calculated using the competing risk method. Cause-specific and overall survival were calculated using the Kaplan-Meier method. Details of locations and number of simultaneous RRs were categorized by lymph node anatomic station. RESULTS: A total of 734 patients were analyzed. The median follow-up was 3.0 years in surviving patients. Four hundred seventy-six (65%) patients had pathologic proof of disease. There were 64 patients with RR. The 2-year local recurrence, RR, and distant metastases rates were 5.6%, 9.0%, and 14.6% respectively. The 2-year cause-specific and overall survival were 89.9% and 63.7%, respectively. There were 136 simultaneous sites of RR. There were 21 recurrences in stations 4R (15.4%), 9 (6.6%) in 4L, 30 (22%) in 7, 19 (13.9%) in 10R, and 14 (10.3%) in 10L. The most common stations for isolated recurrence (n = 19) were station 7 (n = 5; 26.3%) and station 10R (n = 6; 31.6%). The most common RR levels were stations 4 and 7 for right and left upper lobe, stations 5, 7, and 10 for left lower lobe tumors, and stations 7 and 10 for right lower lobe tumors. CONCLUSION: Stations 4, 7, and 10 were the most common stations for RR. These patterns of recurrence may guide nodal staging procedures prior to SBRT.

Matched-Pair Analysis of High Dose Versus Standard Dose Definitive Chemoradiation for Locally Advanced Non-Small-Cell Lung Cancer.

BACKGROUND: Recent data have called into question the use of dose-escalated radiotherapy for locally advanced non-small-cell lung cancer and the effect of cardiac radiotherapy doses. We compared the outcomes after chemoradiation using standard-dose (SD; ≤ 64 Gy) or high-dose (HD; > 64 Gy) radiotherapy. PATIENTS AND METHODS: A matched-pair analysis was performed of 178 patients with stage IIB-IIIB non-small-cell lung cancer for SD versus HD groups using age ± 5 years, gender, stage, tumor size ± 2 cm, yielding 86 patients. The clinical endpoints were estimated using the Kaplan-Meier method. Univariate and multivariate analyses were performed using the Cox regression method. RESULTS: The median follow-up was 16.8 months for the entire cohort (HD, 21.6 months; SD, 12.1 months; P = .06). No significant differences were found in disease stage, histologic type, age, performance status, gender, or tumor size between the 2 groups. The median overall survival was 23.1 months for the HD group (95% confidence interval, 20.6-25.5) versus 13.6 months for the SD group (95% confidence interval, 9.6-17.5; P = .03). The 2-year freedom from locoregional recurrence was 48.7% for the SD and 65.3% for the HD groups (P = .07). The 2-year freedom from distant metastasis was 46.7% for the SD and 70.3% for the HD groups (P = .05). A higher cardiac V30 dose (P = .03) was the strongest predictor of survival besides clinical stage (P = .02). CONCLUSION: Dose-escalated radiotherapy resulted in improved survival and recurrence rates. A higher cardiac dose was a significant predictor of decreased survival.

Changes in Pulmonary Function Following Image-Guided Stereotactic Lung Radiotherapy: Neither Lower Baseline Nor Post-SBRT Pulmonary Function Are Associated with Worse Overall Survival.

PURPOSE: To determine changes in pulmonary function brought about by lung stereotactic body radiation therapy (SBRT). METHODS: One hundred and twenty-seven patients were treated with lung SBRT using 48 to 60Gy in four to five fractions on a prospective trial. We obtained pulmonary function tests (PFTs) at baseline, 6 weeks, 3 months, 6 months, 9 months, 12 months, and 24 months after SBRT. Group mean PFT parameter values are reported. RESULTS: At baseline forced expiratory volume in 1 second (FEV1) was 1.5 l (67% predicted, range: 0.4-3.4 l), corrected diffusing capacity for carbon monoxide was 12.2 ml/min/mmHg (50.8% predicted, range: 3.3-27.2 ml/min/mmHg), and total lung capacity was 5.7 l (102.4% predicted, range: 3.1-9.1 l). At 12 months, there was decline in FEV1 (-4.1%; p = 0.01), corrected diffusing capacity for carbon monoxide (-5.2%; p = 0.027), forced vital capacity (-5.7%; p = 0.004), and total lung capacity (-3.6%; p = 0.039). Declines in FEV1 (-7.6%; p = 0.001) and forced vital capacity (-8.9%; p = 0.001) persisted at 24 months. Rates of pneumonitis were 3.1% and 0.8% for grades 2 and 3, respectively. There were no grade 3 PFT toxicities at 12 months. Lower PFTs at baseline and 1 year after SBRT did not predict for worse overall survival. CONCLUSIONS: As the largest cohort of patients with prospective follow-up PFT evaluation after lung SBRT, this supports the safety of SBRT in this population of predominantly medically inoperable patients. While statistically significant, nearly all declines in PFTs would be rated as a grade 1 on the Radiation Therapy Oncology Group scale, demonstrating safety. PFT declines were not associated with worse overall survival.

Toxicity after central versus peripheral lung stereotactic body radiation therapy: a propensity score matched-pair analysis.

PURPOSE: To compare toxicity after stereotactic body radiation therapy (SBRT) for "central" tumors-within 2 cm of the proximal bronchial tree or with planning tumor volume (PTV) touching mediastinum-versus noncentral ("peripheral") lung tumors. METHODS AND MATERIALS: From November 2005 to January 2011, 229 tumors (110 central, 119 peripheral; T1-3N0M0 non-small-cell lung cancer and limited lung metastases) in 196 consecutive patients followed prospectively at a single institution received moderate-dose SBRT (48-60 Gy in 4-5 fractions [biologic effective dose=100-132 Gy, α/ß=10]) using 4-dimensional planning, online image-guided radiation therapy, and institutional dose constraints. Clinical adverse events (AEs) were graded prospectively at clinical and radiographic follow-up using Common Terminology Criteria for Adverse Events version 3.0. Pulmonary function test (PFT) decline was graded as 2 (25%-49.9% decline), 3 (50.0%-74.9% decline), or 4 (≥75.0% decline). Central/peripheral location was assessed retrospectively on planning CT scans. Groups were compared after propensity score matching. Characteristics were compared with χ(2) and 2-tailed t tests, adverse events with χ(2) test-for-trend, and cumulative incidence using competing risks analysis (Gray's test). RESULTS: With 79 central and 79 peripheral tumors matched, no differences in AEs were observed after 17 months median follow-up. Two-year cumulative incidences of grade ≥2 pain, musculoskeletal, pulmonary, and skin AEs were 14%, 5%, 6%, and 10% (central) versus 19%, 10%, 10%, and 3% (peripheral), respectively (P=.31, .38, .70, and .09). Grade ≥2 cardiovascular, gastrointestinal, and central nervous system AEs were rare (<1%). Two-year incidences of grade ≥2 clinical AEs (28% vs 25%, P=.79), grade ≥2 PFT decline (36% vs 34%, P=.94), grade ≥3 clinical AEs (3% vs 7%, P=.48), and grade ≥3 PFT decline (0 vs 10%, P=.11) were similar for central versus peripheral tumors, respectively. Pooled 2-year incidences of grades 4 and 5 AEs were <1% and 0%, respectively, in both the prematched and matched groups. CONCLUSION: Moderate-dose SBRT with these techniques yields a similarly safe toxicity profile for both central and peripheral lung tumors.

Evaluation of image guided motion management methods in lung cancer radiotherapy.

PURPOSE: To evaluate the accuracy and reliability of three target localization methods for image guided motion management in lung cancer radiotherapy. METHODS: Three online image localization methods, including (1) 2D method based on 2D cone beam (CB) projection images, (2) 3D method using 3D cone beam CT (CBCT) imaging, and (3) 4D method using 4D CBCT imaging, have been evaluated using a moving phantom controlled by (a) 1D theoretical breathing motion curves and (b) 3D target motion patterns obtained from daily treatment of 3 lung cancer patients. While all methods are able to provide target mean position (MP), the 2D and 4D methods can also provide target motion standard deviation (SD) and excursion (EX). For each method, the detected MP/SD/EX values are compared to the analytically calculated actual values to calculate the errors. The MP errors are compared among three methods and the SD/EX errors are compared between the 2D and 4D methods. In the theoretical motion study (a), the dependency of MP/SD/EX error on EX is investigated with EX varying from 2.0 cm to 3.0 cm with an increment step of 0.2 cm. In the patient motion study (b), the dependency of MP error on target sizes (2.0 cm and 3.0 cm), motion patterns (four motions per patient) and EX variations is investigated using multivariant linear regression analysis. RESULTS: In the theoretical motion study (a), the MP detection errors are -0.2 ± 0.2, -1.5 ± 1.1, and -0.2 ± 0.2 mm for 2D, 3D, and 4D methods, respectively. Both the 2D and 4D methods could accurately detect motion pattern EX (error < 1.2 mm) and SD (error < 1.0 mm). In the patient motion study (b), MP detection error vector (mm) with the 2D method (0.7 ± 0.4) is found to be significantly less than with the 3D method (1.7 ± 0.8,p < 0.001) and the 4D method (1.4 ± 1.0, p < 0.001) using paired t-test. However, no significant difference is found between the 4D method and the 3D method. Based on multivariant linear regression analysis, the variances of MP error in SI direction explained by target sizes, motion patterns, and EX variations are 9% with the 2D method, 74.4% with the 3D method, and 27% with the 4D method. The EX/SD detection errors are both < 1.0 mm for the 2D method and < 2.0 mm for the 4D method. CONCLUSIONS: The 2D method provides the most accurate MP detection regardless of the motion pattern variations, while its performance is limited by the accuracy of target identification in the projection images. The 3D method causes the largest error in MP determination, and its accuracy significantly depends on target sizes, motion patterns, and EX variations. The 4D method provides moderate MP detection results, while its accuracy relies on a regular motion pattern. In addition, the 2D and 4D methods both provide accurate measurement of the motion SD/EX, providing extra information for motion management.

Real-time catheter tracking for high-dose-rate prostate brachytherapy using an electromagnetic 3D-guidance device: a preliminary performance study.

PURPOSE: In order to increase the accuracy and speed of catheter reconstruction in a high-dose-rate (HDR) prostate implant procedure, an automatic tracking system has been developed using an electromagnetic (EM) device (trakSTAR, Ascension Technology, VT). The performance of the system, including the accuracy and noise level with various tracking parameters and conditions, were investigated. METHODS: A direct current (dc) EM transmitter (midrange model) and a sensor with diameter of 1.3 mm (Model 130) were used in the trakSTAR system for tracking catheter position during HDR prostate brachytherapy. Localization accuracy was assessed under both static and dynamic analyses conditions. For the static analysis, a calibration phantom was used to investigate error dependency on operating room (OR) table height (bottom vs midposition vs top), sensor position (distal tip of catheter vs connector end of catheter), direction [left-right (LR) vs anterior-posterior (AP) vs superior-inferior (SI)], sampling frequency (40 vs 80 vs 120 Hz), and interference from OR equipment (present vs absent). The mean and standard deviation of the localization offset in each direction and the corresponding error vectors were calculated. For dynamic analysis, the paths of five straight catheters were tracked to study the effects of directions, sampling frequency, and interference of EM field. Statistical analysis was conducted to compare the results in different configurations. RESULTS: When interference was present in the static analysis, the error vectors were significantly higher at the top table position (3.3 ± 1.3 vs 1.8 ± 0.9 mm at bottom and 1.7 ± 1.0 mm at middle, p < 0.001), at catheter end position (3.1 ± 1.1 vs 1.4 ± 0.7 mm at the tip position, p < 0.001), and at 40 Hz sampling frequency (2.6 ± 1.1 vs 2.4 ± 1.5 mm at 80 Hz and 1.8 ± 1.1 at 160 Hz, p < 0.001). So did the mean offset errors in the LR direction (-1.7 ± 1.4 vs 0.4 ± 0.5 mm in AP and 0.8 ± 0.8 mm in SI directions, p < 0.001). The error vectors were significantly higher with surrounding interference (2.2 ± 1.3 mm) vs without interference (1.0 ± 0.7 mm, p < 0.001). An accuracy of 1.6 ± 0.2 mm can be reached when using optimum configuration (160 Hz at middle table position). When interference was present in the dynamic tracking, the mean tracking errors in LR direction (1.4 ± 0.5 mm) was significantly higher than that in AP direction (0.3 ± 0.2 mm, p < 0.001). So did the mean vector errors at 40 Hz (2.1 ± 0.2 mm vs 1.3 ± 0.2 mm at 80 Hz and 0.9 ± 0.2 mm at 160 Hz, p < 0.05). However, when interference was absent, they were comparable in the both directions and at all sampling frequencies. An accuracy of 0.9 ± 0.2 mm was obtained for the dynamic tracking when using optimum configuration. CONCLUSIONS: The performance of an EM tracking system depends highly on the system configuration and surrounding environment. The accuracy of EM tracking for catheter reconstruction in a prostate HDR brachytherapy procedure can be improved by reducing interference from surrounding equipment, decreasing distance from transmitter to tracking area, and choosing appropriated sampling frequency. A calibration scheme is needed to further reduce the tracking error when the interference is high.

Outcomes after stereotactic lung radiotherapy or wedge resection for stage I non-small-cell lung cancer.

PURPOSE To compare outcomes between lung stereotactic radiotherapy (SBRT) and wedge resection for stage I non-small-cell lung cancer (NSCLC). PATIENTS AND METHODS One hundred twenty-four patients with T1-2N0 NSCLC underwent wedge resection (n = 69) or image-guided lung SBRT (n = 58) from February 2003 through August 2008. All were ineligible for anatomic lobectomy; of those receiving SBRT, 95% were medically inoperable, with 5% refusing surgery. Mean forced expiratory volume in 1 second and diffusing capacity of lung for carbon monoxide were 1.39 L and 12.0 mL/min/mmHg for wedge versus 1.31 L and 10.14 mL/min/mmHg for SBRT (P = not significant). Mean Charlson comorbidity index and median age were 3 and 74 years for wedge versus 4 and 78 years for SBRT (P < .01, P = .04). SBRT was volumetrically prescribed as 48 (T1) or 60 (T2) Gy in four to five fractions. Results Median potential follow-up is 2.5 years. At 30 months, no significant differences were identified in regional recurrence (RR), locoregional recurrence (LRR), distant metastasis (DM), or freedom from any failure (FFF) between the two groups (P > .16). SBRT reduced the risk of local recurrence (LR), 4% versus 20% for wedge (P = .07). Overall survival (OS) was higher with wedge but cause-specific survival (CSS) was identical. Results excluding synchronous primaries, nonbiopsied tumors, or pathologic T4 disease (wedge satellite lesion) showed reduced LR (5% v 24%, P = .05), RR (0% v 18%, P = .07), and LRR (5% v 29%, P = .03) with SBRT. There were no differences in DM, FFF, or CSS, but OS was higher with wedge. CONCLUSION Both lung SBRT and wedge resection are reasonable treatment options for stage I NSCLC patients ineligible for anatomic lobectomy. SBRT reduced LR, RR, and LRR. In this nonrandomized population of patients selected for surgery versus SBRT (medically inoperable) at physician discretion, OS was higher in surgical patients. SBRT and surgery, however, had identical CSS.