Risk factors for conversion to mastectomy due to positive margins in early breast cancer patients when choosing breast-conserving surgery: a retrospective cohort study.

BACKGROUND

Breast-conserving surgery (BCS) offers oncologic safety and a superior quality of life for patients with early breast cancer (BC). However, conversion to mastectomy (CMT) owing to positive margins remains unavoidable in some cases. This study explored the risk factors contributing to this issue.

METHODS

This retrospective study analyzed the clinical records of patients who underwent BC surgery between January 1, 2015, and December 31, 2024. Participants were stratified into CMT and BCS groups according to the surgery they received. Demographic and clinical variables were compared between the cohorts. Potential risk factors were assessed using univariable and multivariable logistic regression, and receiver operating characteristic (ROC) curve analysis was used to assess predictive performance.

RESULTS

Among 290 patients (31 in the CMT group and 259 in the BCS group), five parameters demonstrated significant association with CMT in univariable analysis: body mass index (BMI), multifocality, tumor size, false-negative intraoperative frozen section margin, and ductal carcinoma in situ (DCIS) component (P < 0.05). Multivariable logistic regression analysis established four robust predictors of CMT: low BMI (odds ratio [OR] 4.611, P = 0.001), multifocality (OR 4.863, P = 0.026), larger tumor size (OR 3.197, P < 0.001), and DCIS component (OR 5.308, P = 0.035).

CONCLUSIONS

Low BMI, multifocality, larger tumor size, and DCIS components independently predicted CMT in patients undergoing BCS. Although these results should be interpreted with caution, identifying these factors preoperatively may enhance surgical planning and patient outcomes.