Effects of Adjuvant Radiotherapy in Patients With Synovial Sarcoma

To analyze the treatment outcomes and the effects of adjuvant radiotherapy (RT) in patients with synovial sarcoma (SS).The medical records of 103 patients treated with definitive surgery for SS, with/without RT, from August 1982 to July 2013 were reviewed retrospectively. The median age of the patients was 33 years (range, 5 to 72 y). The most frequent tumor location was the extremities (79 patients, 77%). Seventy-five patients (73%) received adjuvant RT and 26 (25%) did not. The median dose of adjuvant RT was 61.2 Gy (range, 45 to 66.6 Gy).The median follow-up period was 5.4 years (range, 0.2 to 31.0 y). The 5- and 10-year overall survival rates were 77 % and 65%, respectively. The progression-free survival (PFS) rates at 5 and 10 years were 52% and 43%, respectively. The most common site of initial failure was the lung (24 patients), followed by local recurrence (14 patients). The 5-year local-recurrence-free survival (LRFS) and distant-metastasis-free survival (DMFS) rates were 80% and 63%, respectively. On multivariate analysis, a mitosis count of <10 per 10 high-power fields (HPF) was a significant predictor of better overall survival, PFS, LRFS, and DMFS (P=0.004, <0.001, 0.025, and <0.001, respectively). Adjuvant RT was an additional prognostic factor for better PFS and LRFS (P=0.006 and 0.028, respectively). A positive/uncheckable resection margin was associated with poor prognosis for DMFS (P=0.011). There was no significant difference in LRFS between the higher and lower RT dose groups (<63 Gy group, 89%; ≥63 Gy group, 88%; P=0.772).The lung and primary site were frequent sites of failure in patients treated with definitive surgery for SS. Adjuvant RT improved LRFS and PFS. Frequent mitotic figures (≥10 mitoses per 10 HPF) were the worst prognostic factor for these patients.