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

PURPOSE: 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.

METHODS AND MATERIALS: 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.

RESULTS

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).

CONCLUSIONS

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.