Adjuvant radiotherapy (adj RT) for extremity and trunk wall atypical lipomatous tumor/well-differentiated LPS (ALT/WD-LPS): A French Sarcoma Group (GSF-GETO) study.

Abstract

10582 Background: The role of adj RT in the management of ALT/WD-LPS remains controversial. Methods: 284 patients (pts) with operable ALT/WD-LPS, no history of previous cancer, CT or RT, treated between 1984 and 2011 and registered in the Conticabase database were included and described. Overall (OS) and local relapse free (LRF) survival were evaluated from the time of first treatment (trt). Their distributions were estimated by Kaplan-Meier method and compared between RT groups using Log-Rank test. Independent prognostic factors and adj RT, were explored with Cox model. Results: Among the 20 centers, 3 enrolled 58% of the pts. Median age at diagnosis was 61 (range 25-94), 146 pts (51%) were males, 223 (79%) pts had distal tumors while 35 (12%) and 26 (9%) had tumors involving the girdle and the trunk wall. The median size of primary tumors was 17 cm (range 2-48), 272 (96%) lesions were deep seated, 24 (9%) were multifocal within the same anatomical area. Surgery quality was unknown for 42 pts. Among the remaining pts, 102 (43%) were R0, 130 (54%) R1 and 8 (3%) R2. Adj RT was given to 129 pts (45%). Pts who received adj RT had larger tumors (p=0.034), involving more often the distal limbs (p<0.001) and were more often multifocal in the same anatomical area (p=0.009). The use of adj RT varied across centers and along the study period. Other characteristics, including margin resection, were balanced between RT groups. Median follow-up for the whole population was 38.6 months (mo) (CI 95% [34.0-47.6]): 51.9 mo [43.0-62.3] for the RT group and 30.7 mo [23.3-37.8] for the surveillance group (Surv). None of the pts developed metastasis during follow-up. With 23 LR, 4 in the RT group and 19 in the Surv group, 3-years LRF rates were 98.8% [91.8-99.8] vs 90.4% [82.3-95.0] with and without adj RT (p<0.001). Once stratified on time period (before/after 2003), adj RT, age and margin resection (R0 vsother) were independently associated with LRFS. No OS difference was observed (p=0.151). Conclusions: In this study, adj RT following resection of ALT/WD-LPS was associated with a reduction of local recurrence risk. More prolonged and homogeneous follow-up is required to confirm these results.