Once-Daily Postmastectomy Radiation Therapy Confers Excellent Locoregional Control for Inflammatory Breast Cancer.

Abstract

For patients with cT4dM0 inflammatory breast cancer (IBC), improved locoregional control has been reported following modern trimodality therapy that includes hyperfractionated/twice-daily postmastectomy radiation therapy (PMRT). We evaluated survival outcomes in a contemporary cohort of patients with IBC routinely treated with once-daily PMRT. We retrospectively identified 213 patients with stage III IBC treated with neoadjuvant systemic therapy, modified radical mastectomy, and PMRT from January 2006 to December 2022 at a single institution. Routinely, PMRT included 50 Gy in 18 to 25 daily fractions to the chest wall and regional nodes with a 0.5 to 1.0 cm skin bolus. We calculated the crude rate of isolated locoregional recurrence (LRR) and estimated disease-free survival (DFS) rates using Kaplan-Meier survival curves and a Cox proportional hazard regression model. Median follow-up was 3.5 years (IQR, 1.8-6.3 years). Isolated LRR was observed in 1.8% (4/213) of patients at a median of 10.6 months (IQR, 8.8-18.4 months). LRR with or without a distant failure occurred in 22 patients (10.3%). All LRRs were observed in patients who did not achieve pathologic complete response (pCR) (n = 148). Distant metastasis occurred in 32% (69/213) of patients, and 57 deaths were recorded. On multivariable analysis, triple-negative subtype (hazard ratio [HR], 3.16; 95% CI, 1.56-6.41; P = .001), lobular histology (HR, 2.45; 95% CI, 1.10-5.45; P = .027), and nodal pCR (HR, 0.27; 95% CI, 0.15-0.49; P < .001) were associated with DFS rates. Subgroup analysis demonstrated no difference in DFS rates between biologic subtypes in patients with pCR (P = .29). Once-daily PMRT confers excellent locoregional control in patients with IBC, as evidenced by low rates of isolated LRR at 3.5 years of follow-up. The worse overall LRR and DFS rates observed in patients with triple-negative subtype and residual nodal disease indicate a need to consider escalating local therapy with a boost while also emphasizing the necessity for novel systemic therapies for IBC.