Neutrophil-to-lymphocyte ratio for the prediction of soft tissue sarcomas response to pre-operative radiation therapy.

PURPOSE/OBJECTIVE: This study aims to assess the prognostic value of the neutrophil-to-lymphocyte ratio (NLR) in soft tissue sarcomas (STS) treated with pre-operative hypofractionated radiotherapy (HFRT). MATERIALS/METHODS: This retrospective analysis included patients treated with pre-operative HFRT of 30 Gy in 5 fractions between 2016 and 2023. Clinical, demographic, and complete blood count (CBC) data were collected. NLR was calculated by dividing the absolute neutrophil count by the absolute lymphocyte count. Only patients with CBCs conducted within 6 months after radiotherapy were included. Cox proportional-hazard regression models were used to assess the impact of NLR and different variables on outcomes. Kaplan Meier were used to illustrate survival curves. A p-value < 0.05 was considered significant, and 95 % confidence intervals (CI) were employed. RESULTS: A total of 40 patients received HFRT and had CBCs within 6 months after radiotherapy. There were 17 (42.5 %) females and 23 (57.5 %) males with a mean age of 66 years. The mean largest tumor size dimension was 7.1 cm, and the mean NLR post-RT was 5.3. The most frequent histological subtypes were myxofibrosarcoma (17.5 %), pleomorphic spindle cell sarcoma (10 %), leiomyosarcoma (7.5 %), and myxoid liposarcoma (5 %). The median follow-up period was 15.4 months. From all patients, 14 patients had disease progression, 12 metastatic disease and 3 died of disease. Multivariable Cox proportional-hazards regression analysis displayed that a higher post-RT NLR was associated with worse disease-free survival (DFS) (HR: 1.303 [1.098-1.548], p = 0.003), and distant metastasis-free survival (DMFS) (HR: 1.38 [1.115-1.710], p = 0.003). Moreover, post-NLR ≥ 4 as a single variable was associated with worse DFS, DMFS, but not worse local recurrence or overall survival. CONCLUSION: This study is the first to evaluate NLR as a prognostic biomarker in STS patients treated with pre-operative radiotherapy. A higher NLR after pre-operative radiotherapy was associated with increased disease progression.

Robust mixed electron-photon radiation therapy planning for soft tissue sarcoma.

BACKGROUND: Mixed electron-photon beam radiation therapy (MBRT) is an emerging technique in which external electron and photon beams are simultaneously optimized into a single treatment plan. MBRT exploits the steep dose falloff and high surface dose of electrons while maintaining target conformity by leveraging the sharp penumbra of photons. PURPOSE: This study investigates the dosimetric benefits of MBRT for soft tissue sarcoma (STS) patients. MATERIAL AND METHODS: A retrospective cohort of 22 STS of the lower extremity treated with conventional photon-based Volumetric Modulated Arc Therapy (VMAT) were replanned with MBRT. Both VMAT and MBRT treatments were planned on the Varian TrueBeam linac using the Millenium multi-leaf collimator. No electron applicator, cutout or additional collimating devices were used for electron beams of MBRT plans. MBRT plans were optimized to use a combination of 6 MV photons and five electron energies (6, 9, 12, 16, 20 MeV) by a robust column generation algorithm. Electron beams in this study were planned at standard 100 cm source-axis distance (SAD). The dose to the clinical target volume (CTV), bone, normal tissue strip and other organs-at-risk (OARs) were compared using a Wilcoxon signed-rank test. RESULTS: As part of the original VMAT treatment, tissue-equivalent bolus was required in 10 of the 22 patients. MBRT plans did not require bolus by virtue of the higher electron entrance dose. CTV coverage by the prescription dose was found to be clinically equivalent between plans of either modality: V 50Gy $V_{\text{50Gy}}$ (MBRT) = 97.9 ± 0.2% versus V 50Gy $V_{\text{50Gy}}$ (VMAT) = 98.1 ± 0.6% (p=0.34). Evaluating the absolute paired difference between doses to OARs in MBRT and VMAT plans, we observed lower V 20Gy $V_{\text{20Gy}}$ to normal tissue in MBRT plans by 14.9 ± 3.2% ( p < 10 - 6 $p<10^{-6}$ ). Similarly, V 50Gy $V_{\text{50Gy}}$ to bone was found to be decreased by 8.2 ± 4.0% ( p < 10 - 3 $p<10^{-3}$ ) of the bone volume. CONCLUSION: For STS with subcutaneous involvement, MBRT offers statistically significant sparing of OARs without sacrificing target coverage when compared to VMAT. MBRT plans are deliverable on conventional linacs without the use of electron applicators, shortened source-to-surface distance (SSD) or bolus. This study shows that MBRT is a logistically feasible technique with clear dosimetric benefits.

Data Dissemination of the Role of Neoadjuvant Radiation in Retroperitoneal Sarcoma: A CTOS and CSSO Survey.

Consensus guidelines call for complete resection of retroperitoneal sarcoma with consideration of neoadjuvant radiation for curative-intent treatment. The 15-month delay from the initial presentation of an abstract to the final publication of the STRASS trial results assessing the impact of neoadjuvant radiation led to a dilemma of how patients should be managed in the interim. This study aims to (1) understand perspectives regarding neoadjuvant radiation for RPS during this period; and (2) assess the process of integrating data into practice. A survey was distributed to international organizations including all specialties treating RPS. Eighty clinicians responded, including surgical (60.5%), radiation (21.0%) and medical oncologists (18.5%). Low kappa correlation coefficients on a series of clinical scenarios querying individual recommendations before and after initial presentation as an abstract indicate considerable change. Over 62% of respondents identified a practice change; however, most also noted discomfort in adopting changes without a manuscript available. Of the 45 respondents indicating discomfort with practice changes without a full manuscript, 28 (62%) indicated that their practice changed in response to the abstract. There was substantial variability in recommendations for neoadjuvant radiation between the presentation of the abstract and the publication of trial results. The difference in the proportion of clinicians describing comfort with changing practice based on the presentation of the abstract versus those that had done so shows that indications for proper integration of data into practice are not clear. Endeavors to resolve this ambiguity and expedite availability of practice-changing data are warranted.

Radiation-Induced Sarcomas of the Breast: A Review of a 20-Year Single-Center Experience.

Background Radiation-induced sarcomas (RISs) are histologically proven sarcomas within or around a previously irradiated site, per Cahan's criteria. RIS incidence is higher in breast cancer compared to other solid cancers and the prognosis remains poor given limited treatment options. This study aimed to review 20-year experience with RISs at a large tertiary care center. Methodology Using our institutional cancer registry database, we included patients meeting Cahan's criteria diagnosed between 2000 and 2020. Patient demographics, oncologic treatment, and oncologic outcomes data were collected. Descriptive statistics were used to describe demographic data. Oncologic outcomes were assessed using the Kaplan-Meier method. Results A total of 19 patients were identified. The median age at RIS diagnosis was 72 years (range = 39-82 months), and the median latency period for the development of RIS was 112 months (range = 53-300 months). All patients underwent surgery, three patients received systemic therapy, and six patients received re-irradiation as salvage treatment. The median follow-up time was 31 months (range = 6-172 months) from the diagnosis of RIS. Overall, five patients had local recurrence, and one patient developed distant metastases. The median time to progression was seven months (range = 4-14 months). The progression-free survival (95% confidence interval (CI)) at two years was 56.1% (37.4-84.4%). At follow-up two years after the diagnosis of sarcoma, the overall survival (95% CI) was 88.9% (75.5-100%). Conclusions While breast RIS remains rare, when managed in a large tertiary care center, overall survival outcomes appear favorable. A significant proportion of patients recur locally after maximal treatment and require salvage therapy to improve outcomes. These patients should be managed in high-volume centers where multidisciplinary expertise is available.

Pathologic Complete Response and Clinical Outcomes in Patients With Localized Soft Tissue Sarcoma Treated With Neoadjuvant Chemoradiotherapy or Radiotherapy: The NRG/RTOG 9514 and 0630 Nonrandomized Clinical Trials.

Importance: Pathologic complete response (pCR) may be associated with prognosis in patients with soft tissue sarcoma (STS). Objective: We sought to determine the prognostic significance of pCR on survival outcomes in STS for patients receiving neoadjuvant chemoradiotherapy (CT-RT) (Radiation Therapy Oncology Group [RTOG] 9514) or preoperative image-guided radiotherapy alone (RT, RTOG 0630) and provide a long-term update of RTOG 0630. Design, Setting, and Participants: RTOG has completed 2 multi-institutional, nonrandomized phase 2 clinical trials for patients with localized STS. One hundred forty-three eligible patients from RTOG 0630 (n = 79) and RTOG 9514 (n = 64) were included in this ancillary analysis of pCR and 79 patients from RTOG 0630 were evaluated for long-term outcomes. Intervention: Patients in trial 9514 received CT interdigitated with RT, whereas those in trial 0630 received preoperative RT alone. Main Outcomes and Measures: Overall and disease-free survival (OS and DFS) rates were estimated by the Kaplan-Meier method. Hazard ratios (HRs) and P values were estimated by multivariable Cox model stratified by study, where possible; otherwise, P values were calculated by stratified log-rank test. Analysis took place between December 14, 2016, to April 13, 2017. Results: Overall there were 42 (53.2%) men; 68 (86.1%) were white; with a mean (SD) age of 59.6 (14.5) years. For RTOG 0630, at median follow-up of 6.0 years, there was 1 new in-field recurrence and 1 new distant failure since the initial report. From both studies, 123 patients were evaluable for pCR: 14 of 51 (27.5%) in trial 9514 and 14 of 72 (19.4%) in trial 0630 had pCR. Five-year OS was 100% for patients with pCR vs 76.5% (95% CI, 62.3%-90.8%) and 56.4% (95% CI, 43.3%-69.5%) for patients with less than pCR in trials 9514 and 0630, respectively. Overall, pCR was associated with improved OS (P = .01) and DFS (HR, 4.91; 95% CI, 1.51-15.93; P = .008) relative to less than pCR. Five-year local failure rate was 0% in patients with pCR vs 11.7% (95% CI, 3.6%-25.1%) and 9.1% (95% CI, 3.3%-18.5%) for patients with less than pCR in 9514 and 0630, respectively. Histologic types other than leiomyosarcoma, liposarcoma, and myxofibrosarcoma were associated with worse OS (HR, 2.24; 95% CI, 1.12-4.45). Conclusions and Relevance: This ancillary analysis of 2 nonrandomized clinical trials found that pCR was associated with improved survival in patients with STS and should be considered as a prognostic factor of clinical outcomes for future studies. Trial Registration: ClinicalTrials.gov Identifiers: RTOG 0630 (NCT00589121); RTOG 9514 (NCT00002791).

Implementation of a DVH Registry to provide constraints and continuous quality monitoring for pediatric CSI treatment planning.

Craniospinal irradiation (CSI) is a complex radiation therapy technique that is used for patients, often children and teenagers/young adults, with tumors that have a propensity to spread throughout the central nervous system such as medulloblastoma. CSI is associated with important long-term side effects, the risk of which may be affected by numerous factors including radiation modality and technique. Lack of standardization for a technique that is used even in larger radiation oncology departments only a few times each year may be one such factor and the current ad hoc manner of planning new CSI patients may be greatly improved by implementing a dose-volume histogram registry (DVHR) to use previous patient data to facilitate prospective constraint guidance for organs at risk. In this work, we implemented a DVHR and used it to provide standardized constraints for CSI planning. Mann-Whitney U tests and mean differences at 95% confidence intervals were used to compare two cohorts (pre- and post-DVHR intervention) at specific dosimetric points to determine if observed improvements in standardization were statistically significant. Through this approach, we have shown that the implementation of dosimetric constraints based on DVHR-derived data helped improve the standardization of pediatric CSI planning at our center. The DVHR also provided guidance for a change in CSI technique, helping to achieve practice standardization across TomoTherapy and IMRT.

Decline in Hepatitis C Virus (HCV) Incidence in Men Who Have Sex With Men Living With Human Immunodeficiency Virus: Progress to HCV Microelimination in the United Kingdom?

BACKGROUND: Modeling of the London hepatitis C virus (HCV) epidemic in men who have sex with men (MSM) and are living with human immunodeficiency virus (HIV) suggested that early access to direct-acting antiviral (DAA) treatment may reduce incidence. With high rates of linkage to care, microelimination of HCV within MSM living with HIV may be realistic ahead of 2030 World Health Organization targets. We examined trends in HCV incidence in the pre- and post-DAA eras for MSM living with HIV in London and Brighton, United Kingdom. METHODS: A retrospective cohort study was conducted at 5 HIV clinics in London and Brighton between 2013 and 2018. Each site reported all acute HCV episodes during the study period. Treatment timing data were collected. Incidence rates and reinfection proportion were calculated. RESULTS: A total of.378 acute HCV infections were identified, comprising 292 first infections and 86 reinfections. Incidence rates of acute HCV in MSM living with HIV peaked at 14.57/1000 person-years of follow-up (PYFU; 95% confidence interval [CI], 10.95-18.20) in 2015. Rates fell to 4.63/1000 PYFU (95% CI, 2.60 to 6.67) by 2018. Time from diagnosis to starting treatment declined from 29.8 (2013) to 3.7 months (2018). CONCLUSIONS: We observed a 78% reduction in the incidence of first HCV episode and a 68% reduction in overall HCV incidence since the epidemic peak in 2015, which coincides with wider access to DAAs in England. Further interventions to reduce transmission, including earlier access to treatment and for reinfection, are likely needed for microelimination to be achieved in this population.

Psychological functioning, coping styles and their relationship to appraisal of physical limitations following invasive surgical procedures for soft-tissue sarcoma: A qualitative study.

BACKGROUND AND OBJECTIVES: This study explored psychological functioning and coping styles in adult patients with soft-tissue sarcoma who underwent surgical procedures in a single expert sarcoma medical center in Canada. METHODS: This is a qualitative study with three formats of data collection. The interview guide was based on theoretical health-related quality of life model. We began the investigation with 2 online and 2 in-person focus groups. Four individual semistructured interviews were added to further explore emerging themes. Data were analyzed using inductive thematic networks approach. RESULTS: Twenty-eight adults (13 female, 24-75 years of age) participated. In the domain of psychological functioning we identified three main themes; changes in mood, worry, and body image concerns. In the domain of coping styles, we identified four adaptive coping styles; positive reframing and optimism, finding a purpose, being proactive, and using humor. Among the maladaptive coping styles, we found passive acceptance, and avoidance and denial. CONCLUSIONS: Psychological well-being can be contingent on physical functioning and coping styles in adults with soft-tissue sarcoma. Both psychological and physical function impact quality of life. Patients with more physical limitations, psychological distress and maladaptive coping styles should be monitored for their well-being.

Statin Use and Risk of Vascular Events Among Cancer Patients After Radiotherapy to the Thorax, Head, and Neck.

Background This study aimed to explore whether statins reduce radiation-induced vascular complications in cancer patients postradiotherapy to the thorax, head, and neck. Methods and Results We conducted a retrospective cohort study within a provincial linked database of 5718 cardiac patients with thorax and head or neck cancer having undergone radiotherapy between 2000 and 2011. One thousand five hundred fifty-two patients were identified as nonstatin users and 4166 as statin users. The primary outcome of interest was the composite of cerebrovascular (transient ischemic attack, and fatal or nonfatal stroke) or cardiovascular events (fatal or nonfatal myocardial infarction). Time-dependent Cox proportional hazard analyses were performed. The crude event rate was 10.31% for nonusers and 9.03% for statin users (hazard ratio of 0.92 [95% CI 0.76-1.10, P=0.3451]), over a mean time to event/censoring of 534±687 days for nonusers and 594±706 days for the statin users. After adjusting for age, sex, prior history of stroke/transient ischemic attack or myocardial infarction, diabetes mellitus, dyslipidemia, atrial fibrillation, chronic kidney disease, heart failure, and hypertension, statin use postradiotherapy was associated with a nonsignificant 15% relative risk reduction, but a strong trend toward reducing the primary outcome (hazard ratio=0.85 95% CI 0.69-1.04, P=0.0811). The use of statins was associated with a significant reduction of 32% for the outcome of stroke alone (hazard ratio=0.68, 95% CI 0.48-0.98, P=0.0368). Conclusions Statin use post radiation therapy was associated with a significant reduction in stroke, with a trend toward significantly reducing cardiovascular and cerebrovascular events.

Are radiation oncologists following guidelines? An audit of practice in patients with uncomplicated bone metastases.

BACKGROUND: Best-practice guidelines recommend single-fraction (SFRT) instead of multi-fraction radiation therapy (MFRT) for uncomplicated symptomatic bone metastases. SFRT is comparable to MFRT in relieving pain, convenient for patients, and cost-effective. Patterns of practice in Canada reveal that SFRT is underused, with significant variability across the country. We audited SFRT use and studied factors that may influence treatment decisions at a large academic tertiary care center in Quebec, Canada. METHODS: Patients who received radiotherapy for uncomplicated bone metastases between February 2014 and March 2015 were reviewed. Age, gender, primary histology, site of metastases and performance status were identified as potential factors affecting fractionation. These were explored by Fisher's test on univariate analysis and logistic regression for multivariate analysis. Retreatment rates were analyzed with cumulative incidence and compared with Gray's test. RESULTS: 254 radiotherapy courses were administered to 165 patients, 85.4% of which were delivered using a single fraction of 8 Gy. Patients age less than 70 years and those with breast histology were more likely to receive MFRT (p = 0.04; p = 0.0046). Performance status (ECOG) was a significant predictor of fractionation because of high correlations between young age, breast histology, and ECOG status (p = 0.03). Follow-up was too short in 40% of patients to derive definitive conclusions on retreatment. CONCLUSIONS: In accordance with current guidelines, our audit confirms that use of SFRT in patients with uncomplicated bone metastases at our center is high. We identified that patient age, primary histology, and performance status influenced fractionation. Incorporation of this quality indicator into our performance dashboard will allow assessment of retreatment differences and other criteria that may also influence treatment choice.

Probabilistic classification of tumour habitats in soft tissue sarcoma.

The purpose of this work is to propose a method to characterize tumour heterogeneity on MRI, using probabilistic classification based on a reference tissue. The method uses maps of the apparent diffusion coefficient (ADC), T2 relaxation, and a calculated map representing high-b-value diffusion-weighted MRI (denoted simDWI) to identify up to five habitats (i.e. sub-regions) of tumours. In this classification method, the parameter values (ADC, T2 , and simDWI) from each tumour voxel are compared against the corresponding parameter probability distributions in a reference tissue. The probability that a tumour voxel belongs to a specific habitat is the joint probability for all parameters. The classification can be visualized using a custom colour scheme. The proposed method was applied to data from seven patients with biopsy-confirmed soft tissue sarcoma, at three time-points over the course of pre-operative radiotherapy. Fast-spin-echo images with two different echo times and diffusion MRI with three b-values were obtained and used as inputs to the method. Imaging findings were compared with pathology reports from pre-radiotherapy biopsy and post-surgical resection. Regions of hypercellularity, high-T2 proteinaceous fluid, necrosis, collagenous stroma, and fibrosis were identified within soft tissue sarcoma. The classifications were qualitatively consistent with pathological observations. The percentage of necrosis on imaging correlated strongly with necrosis estimated from FDG-PET before radiotherapy (R2  = 0.97) and after radiotherapy (R2  = 0.96). The probabilistic classification method identifies realistic habitats and reflects the complex microenvironment of tumours, as demonstrated in soft tissue sarcoma.

Creation of an educational quality improvement program for radiation oncology residents.

PURPOSE: Quality improvement (QI) is a pillar of good clinical governance and is at the center of modern health care. The Royal College of Physicians and Surgeons of Canada mandated, in CanMeds 2015, that QI should be taught and the competencies assessed in all postgraduate residency programs. The objective is to report on the feasibility and impact of teaching QI to radiation oncology residents at a single institution. METHODS AND MATERIALS: A QI team consisting of a clinical fellow, 3 staff physicians, and an expert in QI methods was created within our Department of Radiation Oncology. QI teaching took place in a longitudinal manner, with approximately 12 hours of direct faculty teaching. A mandatory curriculum divided into foundation and intermediate and advanced competencies was devised. Phase 1 teaching, delivered during 2 academic half-days, consisted of didactic lectures, practical workshops, and self-directed online modules. Phase 2 required intermediate-year residents to complete a 9-month QI project. A QI day hosted by the department invited QI experts to teach and enabled residents to present their work, with merit prizes awarded. Our program evaluation used validated assessment tools (self-assessment, QI knowledge-based assessments, and balanced score cards) before and after curriculum implementation and answers quantified using satisfaction indices (SI). RESULTS: Subjective and objective assessments demonstrated improvements in residents' QI knowledge acquisition following curriculum implementation. Those who had completed a project (n = 4) had greater confidence with QI methodology compared with those who had completed phase 1 alone (n = 2) (mean SI, 53% precurriculum to 66.5% and 90%). The majority lacked previous QI teaching and knowledge, but learner attitudes improved (SI, 50%-70%) and 91% of colleagues were enthusiastic about the program being implemented. CONCLUSION: We have demonstrated that implementation of a QI curriculum for radiation oncology residents is feasible and that early results suggesting improvements of attitude and knowledge are positive. We anticipate that the QI skills gained will enable the residents to elevate the quality of their practice throughout their subsequent careers.

Investigating the role of functional imaging in the management of soft-tissue sarcomas of the extremities.

BACKGROUND AND PURPOSE: In this work, we validate a texture-based model computed from positron emission tomography (PET) and magnetic resonance imaging (MRI) for the prediction of lung metastases in soft-tissue sarcomas (STS). We explore functional imaging at different treatment time points and evaluate the feasibility of radiotherapy dose painting as a potential treatment strategy for patients with higher metastatic risk. MATERIALS AND METHODS: We acquired fluorodeoxyglucose (FDG)-PET, fluoromisonidazole (FMISO)-PET, diffusion weighting (DW)-MRI and dynamic contrast enhanced (DCE)-MRI data for 18 patients with extremity STS before, during, and after pre-operative radiotherapy. We tested the lung metastases prediction model using pre-treatment images. We evaluated the feasibility of dose painting using volumetric arc therapy (VMAT) via treatment re-planning with a prescription of 50 Gy to the planning target volume (PTV50Gy) and boost doses of 60 Gy to the FDG hypermetabolic gross tumour volume (GTV60Gy) and 65 Gy to the low-perfusion DCE-MRI hypoxic GTV contained within the GTV60Gy (GTV65Gy). RESULTS: The texture-based model for lung metastases prediction reached an area under the curve (AUC), sensitivity, specificity and accuracy of 0.71, 0.75, 0.85 and 0.82, respectively. Dose painting resulted in adequate coverage and homogeneity in the re-planned treatments: D95% to the PTV50Gy, GTV60Gy and GTV65Gy were 50.0 Gy, 60.3 Gy and 65.4 Gy, respectively. CONCLUSIONS: Textural biomarkers extracted from FDG-PET and MRI could be useful to identify STS patients that might benefit from dose escalation. The feasibility of treatment planning with double boost levels to intratumoural GTV functional sub-volumes was established.

Development and implementation of a radiation therapy incident learning system compatible with local workflow and a national taxonomy.

PURPOSE: Collaborative incident learning initiatives in radiation therapy promise to improve and standardize the quality of care provided by participating institutions. However, the software interfaces provided with such initiatives must accommodate all participants and thus are not optimized for the workflows of individual radiation therapy centers. This article describes the development and implementation of a radiation therapy incident learning system that is optimized for a clinical workflow and uses the taxonomy of the Canadian National System for Incident Reporting - Radiation Treatment (NSIR-RT). METHODS: The described incident learning system is a novel version of an open-source software called the Safety and Incident Learning System (SaILS). A needs assessment was conducted prior to development to ensure SaILS (a) was intuitive and efficient (b) met changing staff needs and (c) accommodated revisions to NSIR-RT. The core functionality of SaILS includes incident reporting, investigations, tracking, and data visualization. Postlaunch modifications of SaILS were informed by discussion and a survey of radiation therapy staff. RESULTS: There were 240 incidents detected and reported using SaILS in 2016 and the number of incidents per month tended to increase throughout the year. An increase in incident reporting occurred after switching to fully online incident reporting from an initial hybrid paper-electronic system. Incident templating functionality and a connection with our center's oncology information system were incorporated into the investigation interface to minimize repetitive data entry. A taskable actions feature was also incorporated to document outcomes of incident reports and has since been utilized for 36% of reported incidents. CONCLUSIONS: Use of SaILS and the NSIR-RT taxonomy has improved the structure of, and staff engagement with, incident learning in our center. Software and workflow modifications informed by staff feedback improved the utility of SaILS and yielded an efficient and transparent solution to categorize incidents with the NSIR-RT taxonomy.

Paediatric radiation oncology in the care of childhood cancer: A position paper by the International Paediatric Radiation Oncology Society (PROS).

Paediatric malignancies are a challenge for the radiation oncologist due to their rarity, the great variety of histological types, and the complexity of treatment concepts that evolve over time. The Paediatric Radiation Oncology Society (PROS) is the only internationally operating society for paediatric radiation oncology. The objectives of PROS are to set a world-wide standard of excellence with respect to radiation oncology aspects in curing children and adolescents with cancer, to provide a forum for communication between radiation oncologists, and to exchange information with all professionals involved in the management of paediatric and adolescent cancer. Challenges include the need to promote education and support practice in low and middle income countries (LMIC) as well as the cost and availability of modern treatment technologies for all but most especially these countries. Collaborations with other societies that include for example the education programmes provided jointly with ESTRO, and the upgraded technical platform of the PROS web site offer new possibilities to enhance the efficacy of PROS in education and support of paediatric radiation oncology practice world-wide. PROS has made an important contribution to the management of childhood malignancies over the past decade and new and developing collaborations between PROS and other societies or organizations will ultimately lead to a reduction in world-wide health care inequalities.

Whole Abdominal-Pelvic Radiotherapy in the Management of Primary Ewing Sarcoma of the Peritoneal Cavity.

Ewing sarcoma of the abdomen is a rare entity in pediatric oncology and represents a technical challenge both for surgeons and radiation oncologists. We document the case of a young female patient with primary disseminated, intraperitoneal Ewing sarcoma who after an excellent response to chemotherapy received preoperative whole abdominal-pelvic radiotherapy with good tolerance.

Margin reduction from image guided radiation therapy for soft tissue sarcoma: Secondary analysis of Radiation Therapy Oncology Group 0630 results.

PURPOSE: Six imaging modalities were used in Radiation Therapy Oncology Group (RTOG) 0630, a study of image guided radiation therapy (IGRT) for primary soft tissue sarcomas of the extremity. We analyzed all daily patient-repositioning data collected in this trial to determine the impact of daily IGRT on clinical target volume-to-planning target volume (CTV-to-PTV) margin. METHODS AND MATERIALS: Daily repositioning data, including shifts in right-left (RL), superior-inferior (SI), and anterior-posterior (AP) directions and rotations for 98 patients enrolled in RTOG 0630 from 18 institutions were analyzed. Patients were repositioned daily on the basis of bone anatomy by using pretreatment images, including kilovoltage orthogonal images (KVorth), megavoltage orthogonal images (MVorth), KV fan-beam computed tomography (KVCT), KV cone beam CT (KVCB), MV fan-beam CT (MVCT), and MV cone beam CT (MVCB). Means and standard deviations (SDs) for each shift and rotation were calculated for each patient and for each IGRT modality. The Student's t tests and F-tests were performed to analyze the differences in the means and SDs. Necessary CTV-to-PTV margins were estimated. RESULTS: The repositioning shifts and day-to-day variations were large and generally similar for the 6 imaging modalities. Of the 2 most commonly used modalities, MVCT and KVorth, there were no statistically significant differences in the shifts and rotations (P = .15 and .59 for the RL and SI shifts, respectively; and P = .22 for rotation), except for shifts in AP direction (P = .002). The estimated CTV-to-PTV margins in the RL, SI, and AP directions would be 13.0, 10.4, and 11.7 mm from MVCT data, respectively, and 13.1, 8.6, and 10.8 mm from KVorth data, respectively, indicating that margins substantially larger than 5 mm used with daily IGRT would be required in the absence of IGRT. CONCLUSIONS: The observed large daily repositioning errors and the large variations among institutions imply that daily IGRT is necessary for this tumor site, particularly in multi-institutional trials. Otherwise, a CTV-to-PTV margin of 1.5 cm is required to account for daily setup variations.