Postoperative Radiotherapy Improved Disease-Free Survival for Low-grade Endometrial Stromal Sarcoma

Abstract

Low-grade endometrial stromal sarcoma (ESS) is a rare gynecological tumor. Surgery is the standard treatment. Whether postoperative radiotherapy reduced disease recurrence rate and brought survival benefits remains controversial. This study was expected to explore the role of postoperative radiotherapy in ESS. This article retrospectively reviewed resected ESS patients with or without postoperative radiotherapy in our center from Jan. 2005 to July. 2018. Adjuvant radiotherapy included external irradiation on pelvic area and brachytherapy to vaginal stump. Hormonal therapy and chemotherapy were administrated to some of the patients. Propensity-matched analysis (PSM) was used to eliminate group difference and Kaplan-Meier survival analysis was done to calculate survival. 132 patients with resected Low-grade endometrial stromal sarcoma were included in the analysis. The median age was 43 years and 90.8% of patients was premenopausal. Stage I and II accounted for most (76.0% and 19.4%, respectively), followed by stage III - IVA. Among all patients, 103 patients underwent bilateral oophorectomy and 5 patients underwent unilateral oophorectomy while the others preserved ovaries. Hormonal therapy was prescribed to 60 (45.5%) patients. A total of 32 (24.2%) patients received postoperative radiotherapy (RT group), while 100 patients did not receive adjuvant radiotherapy (no RT group). The two groups were comparable in age, tumor diameter, stage, menopausal status et al. However, proportion of hormonal therapy (68.8% vs. 38.0%, P = 0.002) and bilateral oophorectomy (90.6% vs. 74.0%, P = 0.048) in the RT group were significantly higher than those in the no RT group. The median follow-up time was 40.5 months. 32 patients relapsed (24.2%, including 22 cases limited to pelvic area, 6 cases relapsed in pelvic and abdominal area, 2 cases relapsed in pelvic area and lungs, 1 case relapsed in pelvic, abdominal area and lungs, 1 case to lungs) and 1 patient (0.8%) died during follow-up. For all patients, 1-year disease-free survival (DFS) was 90.6%, 3 yrs DFS was 79.0%, 5 yrs DFS was 71.2%. Univariate analysis showed that radiotherapy, menopausal status and bilateral oophorectomy significantly prolonged DFS. Postoperative radiotherapy reduced recurrence rate (12.5% (4/32) vs. 27.0% (27/100)). We then did a propensity-matched analysis to eliminate unbalanced factors in RT group and no RT group. A total of 64 patients were matched according to menopausal status, bilateral oophorectomy and hormonal therapy. Kaplan-Meier analysis showed significant improved DFS in RT group compared to no RT group (median DFS: not reached vs. 81monthes, p = 0.004). In terms of toxicity, there was no radiotherapy induced grade III-IV toxicity. In patients with Low-grade endometrial stromal sarcoma after radical resection, postoperative radiotherapy showed significant improvement on DFS which emphasized importance of radiotherapy in ESS.