Inflammatory Response during Neoadjuvant Chemotherapy with Immune Checkpoint Inhibitors in a Patient with T3N1 Triple-Negative Breast Cancer: A Case Report.

Introduction: Preoperative chemotherapy, including immune checkpoint inhibitors (ICIs), is widely accepted as the most likely treatment regimen to obtain a pathological complete response (pCR) in triple-negative breast cancer (TNBC). This case report presents a rare instance of a pCR in a patient with cT3N1M0 TNBC who underwent neoadjuvant chemotherapy (NAC) with ICIs.

Case presentation: We present the case of a 44-year-old woman diagnosed with stage cT3N1M0 TNBC. The patient experienced a gradual enlargement of a left breast mass, axillary lymphadenopathy, and pain. Despite initial NAC with pembrolizumab, paclitaxel, and carboplatin, in addition to pembrolizumab, doxorubicin, and cyclophosphamide, tumor enlargement with an inflammatory response prompted surgical intervention. The patient underwent a left mastectomy with axillary lymph node dissection, resulting in a pCR with no viable tumor cells in the breast or lymph nodes. Postoperative radiotherapy and continued pembrolizumab therapy were administered. After 21 months of follow-up, the patient remains disease-free, with no evidence of recurrence or metastases.

Conclusions: The patient's inflammatory and cystic tumor response is an unreported variant of the NAC response, suggesting the potential for further exploration into the mechanisms driving such responses and their implications for treatment strategies.