A Single-Center Prospective Phase II Study Evaluating the Safety of Omission of Adjuvant Radiotherapy in Young Patients With Low-Risk Ductal Carcinoma In Situ After Breast-Conserving Surgery
This is a single-center, prospective phase II clinical study designed to evaluate whether omission of postoperative radiotherapy is clinically acceptable in young patients with low-risk ductal carcinoma in situ (DCIS) following breast-conserving surgery. Eligible patients include women younger than 40 years with low- or intermediate-grade DCIS, tumor size ≤1 cm, negative surgical margins ≥3 mm, absence of comedo necrosis, and unifocal screen-detected disease. Patients in the radiotherapy omission cohort will undergo close surveillance after surgery, with endocrine therapy permitted according to physician discretion. The primary endpoint is 5-year ipsilateral breast tumor recurrence (IBTR).
• Female patients aged \<40 years；
• Histologically confirmed low- or intermediate-grade ductal carcinoma in situ (DCIS) without invasive carcinoma, including incidental DCIS identified within benign breast lesions；
• Tumor size ≤1 cm on final pathology；
• Negative surgical margins ≥3 mm, including margins obtained after re-excision；
• Unifocal lesion；
• Absence of comedo necrosis；
• Screen-detected disease without bloody nipple discharge or palpable mass；
• Clinically node-negative disease；
• Central pathology review by the participating institution required；
⁃ Ability to understand and willingness to sign written informed consent.