Pembrolizumab + Paclitaxel +/- Bevacizumab for Triple-negative Breast Cancer

* Breast cancer is histologically divided into non-invasive (approximately 10%) and invasive (approximately 90%), with invasive cancer being the target of chemotherapy. Invasive carcinoma is classified into four subtypes according to the expression levels of hormone receptor (HR) and human epidermal growth factor receptor type 2 (HER2). Among them, triple negative breast cancer accounts for 10% of invasive cancers and is the subtype with the poorest prognosis. * For triple negative breast cancer that is operable, chemotherapy with pembrolizumab is administered either preoperatively or postoperatively (perioperative period). For recurrent triple negative breast cancer , combination chemotherapy with multiple agents is the standard of care, especially in the case of PD-L1-positive patients, chemotherapy with an immune checkpoint inhibitor related to PD-1 (pembrolizumab or atezolizumab) is administered. * Although the KEYNOTE355 trial demonstrated the efficacy of pembrolizumab plus paclitaxel therapy in patients with PD-L1-positive triple negative breast cancer in postoperative relapse, this trial did not include patients who received pembrolizumab in the perioperative period. Therefore, it is not known if there is any benefit to re-administering pembrolizumab to these patients after relapse. * Bevacizumab is used as standard therapy for triple negative breast cancer in combination with paclitaxel. Bevacizumab itself is an anti-tumor agent that inhibits angiogenesis, but has also been reported to activate immunity against cancer, suggesting that it may enhance the effect of pembrolizumab.

Based on the above, the investigators planned this trial to evaluate whether pembrolizumab + paclitaxel + bevacizumab therapy is more effective than pembrolizumab + paclitaxel therapy in PD-L1-positive triple negative breast cancer patients who relapse after receiving immune checkpoint inhibitors in the perioperative period.