Pathological complete response with neoadjuvant pembrolizumab and chemotherapy in non-metastatic triple-negative inflammatory breast cancer

Background: The efficacy of neoadjuvant chemoimmunotherapy in patients with non-metastatic triple-negative inflammatory breast cancer (TN-IBC) remains unclear, as patients with IBC have been poorly represented in pivotal clinical trials. Patients and methods: We conducted an observational, retrospective/prospective, multicenter cohort study from 2023 to 2024 of patients with non-metastatic TN-IBC who received at least one cycle of neoadjuvant pembrolizumab plus multi-agent chemotherapy from September 2018 to April 2023. The median follow-up was 1.4 years [95% confidence interval (CI) 1.2-1.7 years]. The primary endpoint was pathological complete response (pCR). Results: Overall, 63 female patients with TN-IBC were included from four cohorts. The most common regimen was pembrolizumab, taxane/carboplatin, and anthracycline/cyclophosphamide (61.9%). Among all patients, 59 (94%) underwent surgery and 4 (6.4%) experienced local and/or distant disease progression during the neoadjuvant treatment. The pCR rate was 31.7% (20/63; 95% CI 20.6% to 44.7%). Conclusions: The combination of neoadjuvant chemotherapy and pembrolizumab resulted in a pCR rate of 31.7% in patients with non-metastatic TN-IBC. Compared with triple-negative non-IBC, the lower pCR rate with this combination regimen highlights the need for biomarkers for better patient selection and more active treatment options for this rare and aggressive breast cancer subtype.