A 56-year-old woman presents for her routine annual mammogram, which reveals suspicious lesions in the upper outer quadrant of the left breast. A stereotactic core needle biopsy confirms high-grade ductal carcinoma in situ (DCIS) with comedo necrosis. The tumor is estrogen receptor-positive (ER+), and she undergoes a lumpectomy to remove the DCIS. What is the standard treatment for ductal carcinoma in situ (DCIS) following a lumpectomy?
