Adjuvant chemotherapy in patients with stage I endometrioid or clear cell ovarian cancer in the platinum era: a Surveillance, Epidemiology, and End Results Cohort Study, 2000-2013

Background: We sought to evaluate the impact of adjuvant chemotherapy on overall survival (OS) in patients with stage I endometrioid epithelial ovarian cancer (EEOC) or ovarian clear cell cancer (OCCC) using a national database. Patients and methods: The Surveillance, Epidemiology, and End Results database was used to identify patients diagnosed with International Federation of Gynecology and Obstetrics (FIGO) stage I EEOC or OCCC from 2000 to 2013. We sought to identify predictors of chemotherapy use and to assess the impact of chemotherapy on OS in these patients. OS was compared using the log-rank test and the Cox proportional hazards model. Results: In all, 3552 patients with FIGO stage I EEOC and 1995 patients with stage I OCCC were identified. Of the 1600 patients (45%) with EEOC who underwent adjuvant chemotherapy, the 5-year OS rate was 90%, compared with 89% for those who did not undergo adjuvant chemotherapy (P = 0.807). Of the 1374 (69%) patients with OCCC who underwent adjuvant chemotherapy, the 5-year OS rate was 85%, compared with 83% (P = 0.439) for those who did not undergo adjuvant chemotherapy. Chemotherapy use was associated with younger age, higher substage, and more recent year of diagnosis for both the EEOC and OCCC groups. Only in the subgroup of patients with FIGO substage IC, grade 3 EEOC (n = 282) was chemotherapy associated with an improved 5-year OS-81% compared with 62% (P = 0.003) in untreated patients (HR: 0.583; 95% CI: 0.359-0.949; P = 0.030). In patients with OCCC, there was no significant effect of adjuvant chemotherapy on OS in any substage. Conclusions: Adjuvant chemotherapy was associated with improved OS only in patients with substage IC, grade 3 EEOC. In stage I OCCC, adjuvant chemotherapy was not associated with improved OS.