Adjuvant chemotherapy and radiation for patients with high-risk stage I endometrial cancer (EC) treated with curative intent surgery: the impact on recurrence and survival

Objectives: Survival benefits of post-operative systemic and radiation therapy in high-risk stage I EC are uncertain. The aim of this study was to compare the patterns and survival outcomes of post-surgical treatment in patients with high-risk stage I EC. Methods: High-risk stage I EC was defined as either stage IB grade 3 endometrioid histology or myo-invasive non-endometrioid histology. Consecutive cases of stage I endometrial carcinoma diagnosed between 2000 and 2010 in 8 cancer centres were included. Patient, disease, and treatment characteristics were summarized by descriptive statistics. Overall survival (OS), disease specific survival (DSS), and relapse free survival (RFS) were calculated by log-rank statistics and Kaplan Meier curves were constructed. Results: Of 2327 patients with stage I EC, high-risk disease accounted for 414. There was heterogeneity among the centres in regards to the extent of surgical staging. Use of chemotherapy (CT) did not improve OS (median 8.52 vs 7.48 years, HR 0.70, 95% CI 0.46-1.14, p=0.13) or DSS (median not reached in both, HR 1.06, 95% CI 0.61-1.85, p=0.84). However, RFS was improved in patients who received CT (median 8.52 vs 6.92 years, HR 0.61, 95% CI 0.39-0.95, p=0.03). Use of radiation therapy (RT) did not improve OS, RFS or DSS. Higher recurrence and lower survivals were noted in patients 55 and over, stage IB, higher grade, and those with lymphovascular space invasion; histology did not impact survival outcomes. Patients who received 4 or less cycles of chemotherapy versus 5-6 cycles had similar OS, DSS, and RFS. Conclusions: Post-operative CT and RT in stage I high-risk endometrial cancer does not improve cancer-specific or overall survival. More than 4 cycles of CT did not improve survival outcomes compared with 4 cycles or less.