The Impact of a Postmastectomy Chest Wall Scar Boost on Local Recurrence-free Survival in High-risk Patients

Abstract

IntroductionA scar boost following postmastectomy radiation to a total dose of > 50 Gy can be considered in cases of invasive breast cancer with high-risk features including advanced tumor stage, lymphovascular space invasion (LVSI), and positive margins. The purpose of this study was to determine the impact of a scar boost on 5-year local recurrence-free survival (LRFS). Materials and MethodsWe retrospectively analyzed 140 patients with invasive breast cancer treated with mastectomy and postmastectomy radiation at a single institution between 2007 and 2016. Patients received 50 to 50.4 Gy to the chest wall and the majority of scar boosts were 9 to 10 Gy. LRFS was examined using the Kaplan-Meier method and univariable Cox regression. ResultsA total of 140 patients met inclusion criteria with a median follow-up time of 48 months. Ninety-four (67.1%) patients did receive a scar boost and 46 (32.9%) patients did not. On subset analysis of patients with LVSI or positive margins, 5-year LRFS was 79.3% in patients treated with scar boost compared with 71.1% in patients without a scar boost (P = .537). In patients with T3 or T4 disease, 5-year LRFS was 80.9% in those who received scar boost and 71.6% in patients who did not (P = .967). The use of a scar boost was not associated with a significant improvement in LRFS on Cox regression (hazard ratio, 0.83; 95% confidence interval, 0.37-1.84; P = .654). ConclusionUse of a scar boost following postmastectomy radiation decreased the absolute percentages of local recurrences in patients with high-risk features; however, this did not translate into a statistically significant benefit.