Adjuvant Radiotherapy Improved Survival in Stage I to II Low-Grade Endometrial Stromal Sarcoma: A Retrospective Study of 152 Cases

OBJECTIVE: Low-grade endometrial stromal sarcoma (LG-ESS) is a rare gynecological tumor. Whether adjuvant radiotherapy benefits survival in patients with resected early-stage ESS remains controversial. This study was designed to explore the role of adjuvant radiotherapy in stage I to II LG-ESS. METHODS: We retrospectively reviewed patients with stage I to II LG-ESS in our center from Jan. 1998 to Feb. 2018. All patients underwent a total hysterectomy and postoperative radiotherapy was administrated based on clinical and pathological characteristics. RESULTS: A total of 152 patients with stage I to II resected LG-ESS were included. Forty patients received adjuvant radiotherapy (RT group) while 112 patients did not receive adjuvant radiotherapy (no RT group). The baseline characteristics of the two groups were comparable, except that the proportion of stage II patients in the RT group was higher than that in the no RT group (32.5% vs. 11.6%, in RT vs. no RT groups, respectively; p = 0.003). For both patient groups, median overall survival was not reached. The median disease-free survival (DFS) was 144 months. Radiotherapy was associated with significantly improved DFS (92 months vs. not reached in RT vs. no RT groups, respectively; p = 0.008) and pelvic failure-free survival (PFFS) (92 months vs. not reached in RT vs. no RT groups, respectively; p=0.004). Subgroup analysis revealed that RT benefited survival most among patients with stage IB to IIB disease. Adjuvant radiotherapy significantly reduced the pelvic recurrence rate (10.0%, 4/40 vs. 28.6%, 32/112, p = 0.018). No radiotherapy-induced grade 4 to 5 toxicity was observed. CONCLUSION: For patients with stage I to II LG-ESS, adjuvant radiotherapy showed significant improvement in DFS and PFFS with tolerable adverse effects, especially in patients with stage IB to IIB disease.