Cytology-negative, non-myoinvasive stage IC serous endometrial cancer: Assessment of adjuvant chemotherapy omission.

Objective: The National Comprehensive Cancer Network clinical practice guidelines suggest possible adjuvant chemotherapy omission for non-myoinvasive stage IC serous endometrial cancers if pelvic cytologic testing shows no malignant cells. Given the limited available data to support this recommendation, this study examined the association between adjuvant chemotherapy omission and survival in patients with cytology-negative, non-myoinvasive stage IC serous endometrial cancers.

Methods: This retrospective cohort study queried the Commission-on-Cancer's National Cancer Database. The study population included patients with non-myoinvasive stage IC serous endometrial cancer who had primary hysterectomy and nodal evaluation from 2010 to 2015. All patients had negative peritoneal cytology. Inverse probability of treatment weighting cohort was created to assess overall survival. Cytology-negative, inner-half myoinvasive stage IIC was evaluated as the proof-of-concept cohort.

Results: In the non-myoinvasive stage IC cohort (n=976), 525 (53.8%) patients did not receive adjuvant chemotherapy. The 10-year overall survival rate for the adjuvant chemotherapy omission group was 11.0% lower compared to the adjuvant chemotherapy treatment group (68.0% versus 79.0%). Hazard risk for all-cause mortality of adjuvant chemotherapy omission compared to adjuvant chemotherapy treatment was 1.54 (95% confidence interval 1.22 to 1.96). In the inner-half myoinvasive stage IIC cohort (n=994), 359 (36.1%) patients did not receive adjuvant chemotherapy. Overall survival for the adjuvant chemotherapy omission group was poorer compared to the adjuvant chemotherapy treatment group (10-year rate 58.0% versus 68.7%, hazard ratio 1.60, 95% confidence interval 1.30 to 1.96).

Conclusions: In this cohort study, adjuvant chemotherapy omission was associated with decreased overall survival for patients with cytology-negative, non-myoinvasive stage IC serous endometrial cancer.