Role of Adjuvant Radiation Therapy After Surgery for Abdominal Desmoplastic Small Round Cell Tumors

Purpose: To identify the prognostic role of adjuvant abdominal radiation therapy (RT) on oncologic outcomes as a part of multimodal treatment in the management of desmoplastic small round cell tumor (DSRCT) and to determine its impact according to the quality of surgical resection. Methods and Materials: All patients treated for primary abdominal DSRCT in 8 French centers from 1991 to 2014 were included. Patients were retrospectively staged into 3 groups: group A treated with adjuvant RT after cytoreductive surgery, group B without RT after cytoreductive surgery, and group C by exclusive chemotherapy. Peritoneal progression-free survival (PPFS), progression-free survival (PFS), and overall survival (OS) were evaluated. We also performed a direct comparison between groups A and B to evaluate RT after cytoreductive surgery. Radiation therapy was also evaluated according to completeness of surgery: complete cytoreductive surgery (CCS) or incomplete cytoreductive surgery (ICS). Results: Thirty-seven (35.9%), thirty-six (34.9%), and thirty (28.0%) patients were included in groups A, B, and C, respectively. Three-year OS was 61.2% (range, 41.0%-76.0%), 37.6% (22.0%-53.1%), and 17.3% (6.3%-32.8%) for groups A, B, and C, respectively. Overall survival, PPFS, and PFS differed significantly among the 3 groups (P<.001, P<.001, and P<.001, respectively). Overall survival and PPFS were higher in group A (RT group) compared with group B (no RT group) (P = . 045 and P =. 006, respectively). Three-year PPFS was 23.8% (10.3%-40.4%) for group A and 12.51% (4.0%-26.2%) for group B. After CCS, RT improved PPFS (P =. 024), but differences in OS and PFS were not significant (PZ. 40 and PZ. 30, respectively). After ICS, RT improved OS (P = .044). A trend of PPFS and PFS increase was observed, but the difference was not statistically significant (PZ. 073 and P = .076). Conclusions: Adjuvant RT as part of multimodal treatment seems to confer oncologic benefits for patients treated for abdominal DSRCT after cytoreductive surgery and perioperative chemotherapy. (C) 2016 Published by Elsevier Inc.