The Impact of Residual Disease After Preoperative Systemic Therapy on Clinical Outcomes in Patients with Inflammatory Breast Cancer.

Background: Inflammatory breast cancer (IBC) is a rare and aggressive disease treated with multimodality therapy: preoperative systemic therapy (PST) followed by modified radical mastectomy (MRM), chest wall and regional nodal radiotherapy, and adjuvant biologic therapy and/or endocrine therapy when appropriate. In non-IBC, the degree of pathologic response to PST has been shown to correlate with time to recurrence (TTR) and overall survival (OS). We sought to determine if pathologic response correlates with oncologic outcomes of IBC patients.

Methods: Following review of IBC patients' records (1997-2014), we identified 258 stage III IBC patients; 181 received PST followed by MRM and radiotherapy and were subsequently analyzed. Pathologic complete response (pCR) to PST, hormone receptor and human epidermal growth factor receptor 2 (HER2) status, grade, and histology were evaluated as predictors of TTR and OS by Cox model.

Results: Overall, 95/181 (52%) patients experienced recurrence; 93/95 (98%) were distant metastases (median TTR 3.2 years). Seventy-three patients (40%) died (median OS 6.9 years). pCR was associated with improved TTR (hazard ratio [HR] 0.20, 95% confidence interval [CI] 0.09-0.46, p < 0.01, univariate; HR 0.17, 95% CI 0.07-0.41, p < 0.0001, multivariate) and improved OS (HR 0.26, 95% CI 0.11-0.65, p < 0.01, univariate). In patients with pCR, grade III (HR 1.91, 95% CI 1.16-3.13, p = 0.01), and triple-negative phenotype (HR 3.54, 95% CI 1.79-6.98, p = 0.0003) were associated with shorter TTR, while residual ductal carcinoma in situ was not (HR 0.85, 95% CI 0.53-1.35, p = 0.48, multivariate).

Conclusions: In stage III IBC, pCR was associated with prognosis, further influenced by grade, hormone receptor, and HER2 status. Investigating mechanisms that contribute to better response to PST could help improve oncologic outcomes in IBC.