Survival Benefit of Adjuvant Radiation Therapy in Node-positive Vulvar Cancer

Background: Adjuvant radiation therapy improves overall survival in patients with vulvar cancer with 2+ positive lymph nodes, but its benefit remains uncertain for 1 positive lymph node. Methods: Using the Surveillance, Epidemiology, and End Results (SEER) database, we identified node-positive, American Joint Committee on Cancer version 6-staged women with squamous cell vulvar carcinoma treated with and without radiation following surgery. The Kaplan-Meier approach assessed overall and cause-specific survival. Propensity score-based, multiply imputed Cox modeling accounted for missing data and selection bias. Results: From 2004 to 2013, 488 versus 206 women did and did not receive adjuvant radiation after surgery. Patient characteristics were well balanced, including home county, index tumor diameter, number of nodes excised, provider type, race, and surgery type (P>0.05). Unbalanced covariates-including median age, grade, number of positive nodes, N-stage-were adjusted using Cox regression. At a median follow-up of 36 months, adjuvant radiation was associated with improved median overall survival across all node-positive patients (54 vs. 24 mo; P<0.01). This survival benefit persisted in women with just one (not reached vs. 39 mo; P<0.01) and 2+ (26 vs. 16 mo; P<0.01) positive lymph nodes. Likewise, all node-positive groups saw a cause-specific survival benefit with adjuvant radiation (all P<0.02). On multivariable Cox regression, adjuvant radiation, age, tumor diameter, number of positive nodes, race, and N-stage associated with survival (P<0.05). Conclusions: All node positive vulvar cancer patients should benefit from and thus should receive adjuvant radiation, including those with one positive node.