Preoperative Immunotherapy Combined With Stereotactic Radiation Therapy Boost in the Treatment of HER2-negative Breast Cancer

This study is testing whether adding immunotherapy (pembrolizumab) and focused radiation therapy (SBRT) before surgery improves outcomes for people with HER2-negative breast cancer. Researchers want to find out if this combination helps shrink the tumor before surgery, increasing the chance of a complete response. **You may be eligible if...** - You are 18 or older with a diagnosis of invasive breast cancer - Your breast cancer is HER2-negative (a specific tumor type) - Your cancer has spread to lymph nodes or is at an advanced local stage - You have not received chemotherapy for your current breast cancer diagnosis - You are generally healthy enough to tolerate standard chemotherapy - Your liver, kidneys, and heart are functioning adequately **You may NOT be eligible if...** - You have inflammatory breast cancer - You are pregnant or breastfeeding - You have HIV, active Hepatitis B or C - You have an autoimmune disease requiring immunosuppressive treatment - You have received prior immunotherapy (anti-PD-1/PD-L1 drugs) - You have had a heart attack or serious heart disease in the past 6 months - You have active tuberculosis or uncontrolled infections Talk to your doctor to see if this trial is right for you.