The Prognostic Significance of p16 Status in Patients With Vulvar Cancer Treated With Vulvectomy and Adjuvant Radiation

Purpose: Vulvar squamous cell carcinoma (VSCC) is a relatively rare malignancy. Human papillomavirus has been implicated as a causative factor for a subset of these patients. The purpose of this study was to evaluate whether p16-positivity (a human papillomavirus surrogate) predicts for better response rates in women who undergo surgery followed by adjuvant radiation therapy (RT). Methods and Materials: We retrospectively analyzed data from women with VSCC who were treated with adjuvant RT. p16-Positivity was defined as diffuse strong immunoreactivity within the tumor. Time to event outcomes was performed with Kaplan-Meier and cumulative incidence methodologies. Results: Thirty-nine women were identified. Ten had positive results for p16 (p16+), and 29 had negative results (p16−). The median follow-up was 25.7 months. The median age at diagnosis was 59 years for women with p16+ tumors and 74 years for women with p16− tumors (P =.022). The distribution of stage did not differ by p16 status. The indications for adjuvant RT were close/positive margins in 19 women, positive nodes in 9 women, and both in 11 women. There were 21 recurrences: 15 vulvar, 3 isolated nodal, 2 synchronous vulvar/nodal, and 1 distant metastasis. In-field relapse rates at 3 years were lower in p16+ patients (32.5%) than in p16− patients (59.1%, P =.072). This trend was also observed in progression-free survival (P =.062). A p16+ status and a lower International Federation of Gynecology and Obstetrics stage were associated with fewer in-field relapses and improved progression-free survival in multivariable analyses. The p16 status was not a predictor of overall survival. Conclusions: p16-Positivity appears to be a prognostic factor for in-field relapse rates in patients with VSCC appropriately treated with adjuvant RT.