Effectiveness of postoperative chemotherapy for stage IC mucinous ovarian cancer

Objective: To examine the association between postoperative chemotherapy and survival of women with stage IC mucinous ovarian cancer (MOC). Methods: Comprehensive nationwide tumor registry data from the Commission on Cancer-accredited facilities in the United States from 2004 to 2014 were retrospectively examined. Women with stage IC MOC who underwent primary surgery followed by postoperative chemotherapy were compared to those who did not receive. Clinico-pathological factors associated with chemotherapy use, and overall survival associated with chemotherapy use were examined with multivariable models and propensity score inverse probability of treatment weighting (IPTW). External validation was performed by examining the Surveillance, Epidemiology, and End Results Program from 1988 to 2014. Results: There were 532 (58.5%) women who received postoperative chemotherapy and 377 (41.5%) women who did not. On multivariable analysis, those with moderately-/poorly-differentiated tumors, large tumor size, and who underwent lymphadenectomy were more likely to receive postoperative chemotherapy whereas young women and those with capsule rupture alone were less likely to receive postoperative chemotherapy (all, P < 0.05). After IPTW, there was no difference in overall survival among women who received postoperative chemotherapy versus those who did not on multivariable analysis (adjusted 4-year rates: 85.8% versus 86.3%, adjusted-hazard ratio [HR] 0.88, 95% confidence interval [CI] 0.60–1.31). Similarly, there was no benefit with chemotherapy regardless of patient age, tumor differentiation, performance of nodal dissection, and substage groups. Among 912 cases in the validation cohort (postoperative chemotherapy use, n = 520 [57.0%]), postoperative chemotherapy use was not associated with cause-specific survival (adjusted-HR 1.296, 95% CI 0.846–1.984, P = 0.233) or overall survival (adjusted-HR 1.131, 95% CI 0.849–1.508, P = 0.400). Conclusion: Postoperative chemotherapy was received by fewer than 60% of women with stage IC MOC, and postoperative chemotherapy was not associated with improved survival.