The Impact of Chest Wall Boost on Reconstruction Complications and Local Control in Patients Treated for Breast Cancer.

[PURPOSE] Giving an additional radiation dose to the incision or chest wall has been a practice, but it has never been studied in a randomized setting, and it might lead to inferior cosmetic outcomes. This study aims to evaluate whether delivery of a chest wall boost (CWB) to the mastectomy scar or chest wall is independently associated with reconstruction complications and to assess its disease control efficacy in the setting of breast reconstruction.

[METHODS AND MATERIALS] We conducted a retrospective chart review of 746 patients with breast cancer who underwent mastectomy, breast reconstruction, and PMRT; all underwent treatment at our institution during 1997 to 2016. Various reconstruction techniques were used among this cohort including autologous reconstruction, single-stage direct-to-implant reconstruction, and 2-stage tissue expander implant. Cohorts were divided by administration of CWB. The primary objective was comparing the rate of reconstruction complications including skin necrosis, fat necrosis and infection between groups. Subgroup analysis for patients with implant-based reconstruction was performed to evaluate the effect of CWB on implant-related complications such as capsular contracture, implant exposure, and implant failure. The secondary objective was comparison of the cumulative incidence of local failure between groups overall and within clinically high-risk subgroups.

[RESULTS] The median follow-up was 5.2 years. Most clinicopathologic features were well balanced between the 379 (51%) patients who received CWB and the 367 (49%) who did not. On multivariate analysis, CWB was significantly associated with infection, skin necrosis, and implant exposure. For implant reconstruction patients, CWB independently increased risks of implant failure. CWB administration was not associated with local tumor control benefits, even in high-risk subgroups.

[CONCLUSIONS] Our findings suggest that omission of chest wall boost in postmastectomy radiation improves breast reconstruction outcomes without compromising local tumor control.