Abstract Book

S168

ESTRO 37

PV-0318 External Validation of Radiation-Induced Dyspnea Models on Esophageal Cancer Radiotherapy Patients Z. Shi 1 , L. Wee 1 , K. Foley 2 , E. Spezi 3 , P. Whybra 3 , T. Crosby 4 , J. Pablo de Mey 5 , J. Van Soest 1 , A. Dekker 1 1 Maastricht University, Department of Radiation Oncology MAASTRO Clinic- GROW – School for Oncology and Development Biology, Maastricht, The Netherlands 2 Cardiff University, Division of Cancer & Genetics, Cardiff, United Kingdom 3 Cardiff University, School of Engineering, Cardiff, United Kingdom 4 Velindre Cancer Centre, Department of Clinical Oncology, Cardiff, United Kingdom 5 Maastricht University, Faculty of Health Medicine and Life Sciences, Maastricht, The Netherlands Purpose or Objective Radiation-induced lung disease (RILD), such as dyspnea, is a risk for patients receiving high-dose thoracic irradiation. This study is a TRIPOD (Transparent Reporting of A Multivariable Prediction Model for Individual Prognosis or Diagnosis) Type 4 validation of previously- published lung toxicity models via secondary analysis of esophageal cancer SCOPE1 trial data. We quantify the predictive performance of these two models for predicting dyspnea 6 months after high-dose chemo- radiotherapy for primary esophageal cancer. Material and Methods Lung cancer patients treated at MAASTRO Clinic (The Netherlands) from the period 2002 to 2011 we re used to develop the previous dyspnea risk models. We tested the performance of the earlier models using baseline, treatment and follow-up data on 258 esophageal cancer patients in the UK enrolled into the SCOPE1 multi-centre trial. As some variables were missing randomly and cannot be imputed, 212 patients in SCOPE1 were used for validation of model 1 and 255 patients were used for validation of model 2. The adverse event of interest was dyspnea ≥ Grade 2 (CTCAE v3) within 6 months of the end of radiotherapy. The model parameter Forced Expiratory Volume in 1s (FEV 1 ) was imputed using the WHO performance status. External validation was performed using an automated, decentralized approach, without exchange of individual patient data. Results Out of 258 patients with esophageal cancer in SCOPE1 trial data, 38 patients developed radiation-induced dyspnea (≥ Grade 2) within 6 months of the end of radiotherapy. Table 1 shows the variables included to develop the lung toxicity models, and their Area Under Curve (AUC) scores in the previous study and on the SCOPE1 data. In addition, the receiver operator curves (ROCs) of using both models on the external validation set of the SCOPE1 are shown in Figure 1 . The curves and AUCs derived by distributed learning were identical to the results from validation on a local host.

Conclusion We have externalyl validated previously published dyspnea models using an esophageal cancer dataset. FEV 1 that is not routinely measured in esophageal cancer was imputed using WHO performance status. The prediction performance of the models in esophageal cancer patients treated with high-dose external beam radiotherapy was moderate, AUC of 0.66 (95% CI 0.54 – 0.75.) and 0.68 (95% CI 0.58 -0.77), respectively. Prediction performance was not statistically different from previous training and validation sets, therefore a common thoracic RILD model should be feasible despite a different primary tumor. Risk estimates were strongly determined by WHO score in Model 1 and baseline dyspnea in Model 2. The distributed learning approach gave the same answer as local validation, but is feasible without accessing a validation site’s individual patients-level data. PV-0319 A systematic review and quantitative synthesis of tolerance doses for distinct late toxicities C. Olsson 1 , M. Thor 2 1 University of Gothenburg, Regionalt Cancercentrum RCC väst, Gothenburg, Sweden 2 Memorial Sloan Kettering Cancer Center, Medical Physics, New York, USA Purpose or Objective To 1.) Systematically review tolerance doses for late toxicity following external beam radiotherapy (EBRT) and treatments involving brachytherapy (BT) for prostate cancer in the post-Emami/QUANTEC era with a special emphasis on distinct late gastrointestinal, genitourinary, and sexual dysfunction symptoms (GI/GU/SD), and 2.) Perform a quantitative synthesis of identified dose- volume histogram thresholds (DVH t ). Material and Methods The inclusion criteria for full-text articles published since the Emami paper and the QUANTEC reports were: randomized controlled/case-control/cohort studies with non-aggregated symptom assessments, follow-up time ≥3 months, >20 patients, and primary photon-based treatments for localized prostate cancer with DVH data. The DVH t were converted into equivalent doses in 2Gy fractions (EQD2; GI+SD/GU:α/β=3Gy/6Gy). Within the quantitative synthesis for each symptom, a polynomial function was first fitted to all DVH t (agreement between DVH t : R 2 ), and for symptoms with ≥3 DVH t from ≥2 studies, 2-3 across-studies cohering DVH t (COMT DVHs ) were then identified (cf. equal-weight computational center- of-mass). The review was registered at PROSPERO. Results From 33 studies that fulfilled the inclusion criteria, the majority of DVH t were derived after EBRT and primarily for GI toxicity (N thresholds GI/GU/SD: 97/8/1). Among these five symptoms – Defecation urgency (DU), Diarrhea (DI), Fecal incontinence (FI), Proctitis (P) and Rectal bleeding (RB) – presented with DVH t with reasonable agreement