Prognostic Significance of Lymph Node Ratio in Ovarian Cancer

Lymphadenectomy is critical in the clinical prognosis of ovarian cancer patients. Therefore, we assessed whether lymph node ratio (LNR) has predictive value on overall survival (OS) of patients with serous epithelial ovarian cancer (SEOC). A total of 7,815 eligible SEOC patients were identified from the Surveillance, Epidemiology, and End Results (SEER) database, who underwent surgical resection between 1973 and 2013. We used the time-dependent receiver operating characteristic (ROC) curve and the area under curve to determine the optimal cut-off value of LNR. The predictive role of LNR was analyzed by Cox proportional hazards regression model. The effects of LNR and positive lymph nodes (PLN) on OS were evaluated by comparing the time-dependent ROC curves. The time-dependent ROC curves showed that the optimal LNR cut-off value was 42.0% for nodal-positive SEOC. As shown in Kaplan-Meier survival curves, survival was significantly poorer for all patients with LNR≥42.0% (log-rank test: P<0.0001), regardless of the stage. In the multivariate Cox analysis, LNR≥42.0% remained a significant and independent predictor of mortality risk for all patients [hazards ratio: 1.526, 95% confidence interval: 1.415-1.647; P<0.0001], compared with those LNR<42.0%. These results suggest that LNR, rather than the number of PLN or stage, could be regarded as a promising predictor of mortality risk, particularly in stage-III SEOC patients.