Multidisciplinary Tumor Board Decision Making for Postoperative Radiotherapy in Thymic Epithelial Tumors: Insights from the RYTHMIC Prospective Cohort

Introduction Thymic epithelial tumors (TETs) are rare intrathoracic malignancies for which surgery represents the mainstay of the treatment. Current practice for postoperative radiotherapy (PORT) is highly variable, and there is a lack of prospective, high level evidence. Réseau Tumeurs Thymiques et Cancer (RYTHMIC) is the nationwide network for TETs in France. Established in 2012, it prospectively collects data on all TET patients, for whom management is discussed at a national multidisciplinary tumor board (MTB). We assessed whether PORT decisions at the MTB were in accordance with RYTHMIC guidelines and ultimately implemented in patients. Methods All consecutive patients for whom PORT was discussed at the MTB from 2012 to 2015 were identified from the RYTHMIC prospective database, and a complete review of their medical records was performed. Results A total of 274 patients, including 243 with thymoma (89%) and 31 with thymic carcinoma (11%), were analyzed. The decision of the MTB was in accordance with guidelines in 221 patients (92%) of the 241 with stage I or III TET. An MTB decision to deliver PORT was made for 117 patients (43%). PORT was ultimately initiated in 101 patients. The most frequent reason for not delivering PORT was excessive (>3 months) delay after surgery. Dose-volume constraints defined by the International Thymic Malignancy Interest Group were followed in all but four patients. Conclusion Our data provide a unique insight into the decision-making process for PORT in TETs, highlighting the need for systematic discussion at an expert MTB, while stressing the value of current available guidelines.