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.