Evaluating and Monitoring Immune and Clinical Responses in Early-Stage Triple Negative Breast Cancer Undergoing Neoadjuvant Chemo-immunotherapy With Pembrolizumab

This study closely monitors how the immune system responds in women with early-stage triple-negative breast cancer (TNBC) who are receiving standard chemo-immunotherapy with pembrolizumab before surgery. It collects blood and tissue samples to better understand which patients benefit most from this treatment. **You may be eligible if...** - You have newly diagnosed, previously untreated stage II or III invasive breast cancer - Your cancer is triple-negative (ER-negative, PR-negative, HER2-negative) - You have not received any prior chemotherapy, hormone therapy, or immunotherapy for this cancer - You are willing and able to follow the study schedule **You may NOT be eligible if...** - You are pregnant, breastfeeding, or unwilling to use birth control - You are taking steroids (such as prednisone or dexamethasone) beyond what is prescribed as part of the study regimen - You are enrolled in another experimental treatment study - You have HIV on antiretroviral therapy - You have an uncontrolled infection, heart problem, or psychiatric condition that affects compliance Talk to your doctor to see if this trial is right for you.