The goal of this observational study is to analyze clinicopathological characteristics and identify independent prognostic risk factors, as well as compare treatment outcomes in female patients aged ≥18 years with pathologically confirmed local recurrence of breast cancer after radical surgery (breast-conserving surgery or total mastectomy) without distant metastasis. The main questions it aims to answer are:

What clinical and pathological factors independently affect progression-free survival (PFS) and overall survival (OS) of breast cancer patients with postoperative local recurrence? Do clinical features and long-term prognosis differ between patients with local recurrence after breast-conserving surgery and those after total mastectomy? Can we identify optimal individualized treatment regimens and suitable populations for re-breast-conserving surgery and postoperative radiotherapy after R0 resection?

Participants will:

Provide complete baseline demographic, initial clinicopathological, primary surgical and adjuvant treatment data, local recurrence lesion characteristics and post-recurrence treatment information via standardized case report forms; Undergo routine clinical examinations, imaging reviews and pathological rechecks as standard clinical practice; Receive standardized follow-up for at least 3 years through outpatient visits supplemented by telephone/WeChat contact to record disease progression, secondary local recurrence, distant metastasis, all-cause death and treatment adverse events.

This is a single-center, prospective, non-interventional cohort study. It aims to analyze the clinicopathological characteristics of female patients with isolated local recurrence without distant metastasis after radical breast cancer surgery, identify independent prognostic risk factors affecting progression-free survival (PFS) and overall survival (OS), compare the clinical features and long-term prognostic differences between patients with local recurrence after breast-conserving surgery and those after total mastectomy, and explore eligible populations and optimal individualized treatment strategies after local recurrence. Female patients treated at the Department of Breast Surgery, Jiangsu Provincial People's Hospital, aged ≥18 years, pathologically confirmed to have postoperative local breast cancer recurrence without distant metastasis, tolerant to anti-tumor therapy and capable of completing full follow-up will be consecutively enrolled, and all subjects will sign informed consent forms. Baseline demographic data, primary clinicopathological information, initial surgical and adjuvant treatment records, characteristics of recurrent lesions, and comprehensive treatment data after local recurrence will be uniformly collected to establish a standardized electronic database with double-data entry for quality control. Standardized follow-up of at least 3 years will be conducted starting from the date of confirmed local recurrence, mainly through outpatient reexaminations supplemented by telephone and WeChat follow-up. Endpoint events including secondary local recurrence, distant metastasis, all-cause death and treatment-related adverse reactions will be recorded. Statistical analyses will be performed using SPSS 26.0 and R 4.3.0. Kaplan-Meier survival analysis and the Log-rank test will be adopted for univariate prognostic comparison. Multivariate Cox regression and Logistic regression models will be constructed to screen independent influencing factors. Subgroup and interaction analyses will be carried out stratified by initial surgical modality, molecular subtype, recurrence interval and lesion size. A prognostic nomogram prediction model will be developed based on regression models, with its discrimination and calibration validated. This study will not interfere with routine clinical treatment regimens; all patients will receive treatment in accordance with domestic breast cancer guidelines and institutional MDT standards. All research data will be anonymized throughout the study. After follow-up completion, data will be locked uniformly, and multiple imputation and sensitivity analyses will be performed to ensure robust results. The findings of this study can provide prospective evidence for risk stratification, prognostic assessment and the formulation of individualized treatment regimens for breast cancer patients with postoperative local recurrence.

Inclusion Criteria:

1. Patients with a prior history of breast-conserving surgery or total mastectomy, with postoperative pathological diagnosis of invasive breast carcinoma or ductal carcinoma in situ (DCIS);
2. Pathologically confirmed isolated local recurrence of breast cancer after primary surgery, without evidence of distant metastasis;
3. Aged ≥ 18 years old; Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1, and eligible to receive reoperation and subsequent anti-tumor therapy;
4. Voluntarily participate in this study and provide written informed consent.

Exclusion Criteria:

1. Presence of concurrent distant metastasis at the time of breast cancer local recurrence;
2. Severe dysfunction or failure of vital organs (cardiac, hepatic, renal, etc.) that contraindicates reoperation or systemic anti-tumor treatment;
3. Inability to complete scheduled long-term follow-up as required by the study.

This single-center prospective observational cohort enrolls female patients aged ≥18 years from the Department of Breast Surgery, Jiangsu Provincial People's Hospital. Eligible participants previously received breast-conserving surgery or total mastectomy for pathologically confirmed invasive breast carcinoma or ductal carcinoma in situ (DCIS), with newly pathologically proven isolated local breast cancer recurrence and no distant metastasis. Subjects must have ECOG performance status 0 or 1 to tolerate salvage reoperation and anti-tumor therapy, and sign written informed consent voluntarily. Patients are excluded if they have concurrent distant metastasis at recurrence, severe cardiac, hepatic, renal or other vital organ dysfunction that prevents treatment, or fail to comply with long-term follow-up.

The individual participant data involves sensitive personal clinical information of patients, and there is no established data sharing protocol approved by the ethics committee for external researchers at present. Therefore, IPD will not be shared after the study is finished.