Mismatch repair status and surgical approach in apparent early-stage endometrial cancer.

Objective: To test the hypothesis that mismatch repair (MMR) status (as an accurate surrogate marker for microsatellite stability) modifies the effect of surgical approach on oncological outcome for apparent early-stage endometrial cancer.

Methods: Observational data from a large prospective population study on endometrial cancer were analyzed using target trial methodology and doubly robust methods, including propensity score matching and adjusted regression analyses. Laparoscopy was compared with laparotomy, stratified by MMR status on outcomes of recurrence and site, and recurrence-free, overall, and disease-specific survival.

Results: After matching, there were 400 patients for analysis, with 200 in each treatment group. The mean age was 62 years and mean body mass index was 32 kg/m. Most patients had early-stage disease (stage I n=362 (90%)) and endometrioid histology (n=363 (91%)). Adjuvant pelvic radiation was administered to 11%, adjuvant vaginal brachytherapy to 13% and adjuvant chemotherapy to 5% of patients. Five-year recurrence-free survival did not differ significantly between modes of surgery across the cohort (p=0.7) or within MMR strata (MMR-proficient p=0.9, MMR-deficient p=0.6). Similarly, there was no significant difference in overall or disease-specific survival by mode of surgery across the cohort or within MMR strata. There was no significant difference in the HR for recurrence for those treated with laparoscopy stratified by MMR status (MMR-proficient HR=0.99 (95% CI 0.28 to 3.58); MMR-deficient HR=0.83 (95% CI 0.24 to 2.87)), even when restricted to endometrioid subtype.

Conclusion: In this study, there was no evidence of a difference in survival outcomes according to mode of surgery and MMR status.