Phase II Clinical Trial of PD-L1 in Combination With Vinorelbine + Cyclophosphamide + Capecitabine (VEX) Metronomic Chemotherapy With or Without Radiotherapy for Advanced Triple-negative Breast Cancer.

This study is testing a combination of an immunotherapy drug (a PD-L1 inhibitor) with low-dose metronomic chemotherapy (vinorelbine, cyclophosphamide, and capecitabine, given in small regular doses) with or without radiotherapy for people with advanced triple-negative breast cancer (a type that is harder to treat because it lacks the three most common receptors targeted by breast cancer drugs). **You may be eligible if...** - You are 18 or older (male or female) - You have confirmed metastatic triple-negative breast cancer - Your cancer diagnosis is documented with clinical data - You have measurable disease on imaging **You may NOT be eligible if...** - You have already received certain prior treatments that would interfere with the study - You have active brain metastases - You have severe heart, liver, or kidney problems - You are pregnant or breastfeeding Talk to your doctor to see if this trial is right for you.