Safety of Breast-Conserving Surgery for Multifocal or Multicentric Breast Cancer

This single-center, single-arm prospective observational cohort study enrolls female patients aged ≥18 years with unilateral multifocal or multicentric breast cancer treated at the Department of Breast Surgery, the First Affiliated Hospital of Nanjing Medical University. Subjects are screened in strict accordance with unified inclusion and exclusion criteria. All enrolled patients receive breast-conserving surgery followed by standardized postoperative radiotherapy and individualized adjuvant therapy without trial-specific interventions, and all treatment regimens are formulated in line with domestic guidelines for breast cancer diagnosis and treatment. All participants sign written informed consent prior to enrollment. Uniform baseline data including demographic characteristics, menstrual and reproductive history, family history of malignancy, imaging findings, pathological profiles, molecular subtypes, and surgical information are collected. Postoperative 30-day surgical complications are documented to evaluate short-term surgical safety. Standardized long-term follow-up lasting no less than 3 years is conducted after surgery via outpatient visits, telephone calls and WeChat communication to continuously track oncological endpoints such as ipsilateral breast tumor local recurrence, regional lymph node recurrence, contralateral breast malignancy and distant metastasis, as well as data on disease-free survival and overall survival. Validated standardized questionnaires including Breast-Q, SDS, SAS and EORTC QLQ-C30 are administered at scheduled follow-up time points to assess patients' satisfaction with breast appearance, anxiety and depression status, and overall quality of life. All data are double-entered, subjected to regular quality control and anonymized for privacy protection. Statistical analyses consist of descriptive statistics, univariate analyses, multivariate Logistic regression, Cox proportional hazards regression, and Kaplan-Meier survival analysis. Subgroup analyses stratified by molecular subtype, lesion distribution pattern and axillary lymph node status are performed, and a nomogram predicting the risk of postoperative local recurrence is constructed to facilitate individualized clinical risk assessment. Patients with inflammatory breast cancer, extensive lesions precluding negative surgical margins, severe vital organ dysfunction, pregnancy or lactation incompatible with radiotherapy, or inability to complete long-term follow-up are excluded from the study. Lost-to-follow-up cases are treated as censored data in survival analyses, and baseline characteristics are compared between lost and fully followed patients to mitigate attrition bias. This study receives no external funding. All study procedures strictly comply with the Declaration of Helsinki and institutional ethical review requirements. The study aims to clarify the oncological safety of comprehensive breast-conserving therapy for multifocal or multicentric breast cancer, identify independent risk factors for postoperative local recurrence, and provide native evidence-based references for individualized surgical management of such patients in China.