IMRT is Associated with Lower Reconstruction Failure and Complication Rates Following Post-Mastectomy Radiation to a Reconstructed Breast

Abstract

An increasing percentage of breast cancer patients receive post-mastectomy radiation with a reconstruction in place, as immediate reconstruction has become more prevalent. Post-mastectomy radiation can improve survival, but also impact reconstruction outcomes. We investigated the impact of intensity modulated radiation therapy (IMRT) on reconstruction failure and complication rates compared with conventional radiation (CRT). A prospectively-collected institutional database was queried for women with stage I-III breast cancer treated 2000-2018, undergoing mastectomy, immediate reconstruction, and radiation to the reconstructed breast within 1 year of surgery. Patients were stratified into IMRT and CRT groups based on post-mastectomy radiation technique. Reconstruction failure was defined as complication requiring surgical revision or removal of the reconstruction. Complications were defined as infection, contracture, necrosis, or fibrosis. Covariates of interest included age, race, BMI, smoking status, stage, histology, hormonal status, HER2 status, systemic therapy type and timing, use of nodal radiation, and time to start of radiation. Differences in characteristics and complication crude rates were assessed with Chi-square or Fishers exact tests. Competing risk regression was used to estimate hazard ratios; covariates were included one at a time to avoid overadjustment. Cumulative incidence curves were estimated for time to first complication and compared using Gray’s test. A total of 206 breast cancers in 202 patients were included, with 139 in the IMRT group and 67 in the CRT group. Median follow up was 45 months (range 4-210), and patient cohorts were generally similar. Overall, reconstruction failure (6.9%) and complication (11.4%) rates were low. The IMRT group had significantly lower rates of reconstruction failure (2.9% vs 15.6%, p=0.002) and complications (5.8% vs 23.4%, p<0.001) compared to the CRT group. On univariate analysis, use of CRT was strongly predictive of reconstruction failure (HR 4.82, p=0.007) and complication (HR 3.89, p=0.002), and significance persisted on multivariable analysis, after adjusting separately for other significant predictors including age, post-menopausal status, implant reconstruction, chemotherapy, and time to start of radiation (failure: adjusted HR= 4.2 to 5.6, all p<0.05; complication: adjusted HR=3.4 to 4.1, all p<0.01). Survival outcomes were similar, with no difference in overall (p=0.12) and progression free (p=0.41) survival and similar distribution of locoregional and distant failures. Post-mastectomy IMRT can improve reconstruction outcomes over CRT, with significantly lower reconstruction failure and complication rates and no survival difference. Increasing the use of IMRT can make radiation to a reconstructed breast safer for patients and potentially broaden the population eligible for immediate reconstruction.