Study on the Use of Lateral Decubitus Position in Left Breast Cancer Patients Undergoing Adjuvant Radiotherapy

This study is testing whether lying on your side (lateral decubitus position) during radiation therapy planning and delivery improves the accuracy of radiation targeting for women with left-sided breast cancer, potentially reducing radiation exposure to the heart. **You may be eligible if...** - You are a woman between 18 and 70 years old - You have been newly diagnosed with left-sided breast cancer (confirmed by pathology) - You have had a mastectomy or breast-conserving surgery - Your cancer has not spread to distant parts of the body - Your overall health is good to moderate (ECOG 0, 1, or 2) **You may NOT be eligible if...** - You have cancer in both breasts - You have had breast reconstruction or implant placement on the affected side - You have previously received radiation to the chest or collarbone area Talk to your doctor to see if this trial is right for you.