Stage IC grade 1 endometrioid adenocarcinoma of the ovary: assessment of post-operative chemotherapy de-escalation

Abstract

Objective Given limited real-world practice data evaluating the National Comprehensive Cancer Network clinical practice guidelines for possible post-operative chemotherapy omission as a treatment option for patients with stage IC grade 1 endometrioid ovarian carcinoma, this population-based study examined the association between post-operative chemotherapy and overall survival in this tumor group. Methods The National Cancer Institute’s Surveillance, Epidemiology, and End Results program was retrospectively queried. The study population was 1207 patients with stage IC grade 1–3 endometrioid ovarian carcinoma who received primary cancer-directed surgery from 2007 to 2020. Overall survival was assessed with multivariable Cox proportional hazard regression model. Results The median age was 52, 54, and 55 years for grade 1, 2, and 3 groups, respectively (p=0.02). Grade 1 and 2 tumors were more common than grade 3 tumors (n=508 (42.1%), n=493 (40.8%), and n=206 (17.1%), respectively). Chemotherapy use rate for grade 1 tumors was lower compared with grade 2–3 tumors (67.9%, 76.5%, and 78.6%, respectively, p<0.001). When nodal evaluation was performed for grade 1 tumors, among patients who did not receive post-operative chemotherapy and among those who did, 5-year overall survival rate exceeded 90% (93.3% and 96.0%, respectively), with statistically non-significant hazard estimates (adjusted hazard ratio (aHR) 1.54, 95% CI 0.63 to 3.73). In contrast, post-operative chemotherapy omission for patients who did not undergo nodal evaluation was associated with decreased overall survival (5-year rates 82.3% vs 96.0%, aHR 5.41, 95% CI 1.95 to 15.06). Results were similar for node-evaluated grade 2 tumors (5-year overall survival rates, 94.6% and 94.4% for node-evaluated post-operative chemotherapy omission and administration, respectively), but not in grade 3 tumors. Conclusion The results of this population-based study may partially support the current clinical practice guidelines for post-operative chemotherapy omission as a possible option for patients with stage IC grade 1 endometrioid adenocarcinoma of the ovary for those who had lymph node evaluation. Observed data were also supportive for node-evaluated grade 2 tumors, warranting further evaluation.