PDCD1 and breast carcinoma: In a phase 2 clinical trial of metronomic chemotherapy combined with PD-1 inhibitors for the treatment of breast cancer, the group receiving metronomic cyclophosphamide, capecitabine, and metronomic vinorelbine combined with toripalimab showed a higher disease control rate (DCR) of 69.7% and a longer median progression-free survival (PFS) of 6.6 months compared to the other groups (4).