Dose-escalated intensity modulated radiation therapy in patients with locally-advanced vulvar cancer - does it increase response rate?

Abstract

Purpose: GOG 205 safely increased clinical (cCR) and pathologic complete response (pCR) in locally-advanced vulvar cancer through dose escalation using three-dimensional radiotherapy (RT). The aim of this study is to assess the response of dose-escalated intensity modulated radiotherapy (IMRT) in locally-advanced vulvar cancer.

Methods: A retrospective review of patients treated with dose-escalated (≥ 55Gy) IMRT from 2012 to 2018 for locally-advanced vulvar cancer was performed. Patients treated with preoperative or definitive intent were included. Rates of cCR and pCR were assessed, and predictors of disease-free survival (DFS) were analyzed using the Kaplan Meier method with log rank test between groups and a parsimonious multivariate Cox model.

Results: Median dose to the vulva was 66.0 Gy (Interquartile Range [IQR]: 66.0-68.0) for definitive and 59.4 Gy (IQR: 58.0-59.4) for preoperative IMRT. The overall rates of cCR and pCR were 76% and 70%, respectively. DFS at two years was 65% (95% Confidence Interval [CI] 50-80%) for all patients, 81% (95% CI 63% - 98%) for definitive IMRT, and 55% (95% CI 35% - 76%) for preoperative IMRT. On multivariate analysis, cCR predicted for disease-free survival (HR 0.21; 95% CI 0.06-0.76; p = 0.02), and pCR predicted for OS (HR 0.12; 95% CI 0.02-0.60; p = 0.01). Grade 3 acute and late RT toxicity was seen in 14 (29%) and 3 (6%) of patients, respectively.

Conclusion: Dose-escalated IMRT for locally-advanced vulvar cancer is well tolerated, with rates of cCR and pCR that compare favorably with published data.

Keywords: Dose-escalated; Groin recurrence; IMRT; PCR; Radiation; Vulvar cancer.