Clinico-pathological features predicting indication to mastectomy in breast cancer patients achieving complete response after neoadjuvant therapy: A retrospective analysis of the EUSOMA database

Aims: We investigated factors related to the type of surgery, i.e. mastectomy versus breast conserving surgery (BCS), in breast cancer (BC) patients with complete pathologic response in the breast (ypT0) after neoadjuvant therapy (NAT). Methods: A retrospective analysis from the EUSOMA database was performed using data from 55 certified centers across 14 European countries, including ypT0 BC patients (i.e., neither invasive nor in situ residuals), treated between 2017 and 2022. Variables analyzed included year of surgery, age, number and distribution of tumor focality, extent, clinical and pathological stages, and biologic subtype. Logistic regression was used to identify predictors of surgical choice. The Kaplan-Meier method was used for comparison of local recurrence-free survival (LRFS) between surgical groups. Results: Of 1416 BC patients included, 67.5 % underwent BCS and 32.5 % mastectomy. At multivariable analysis, factors increasing the likelihood of mastectomy included: more recent year of surgery [odds ratio (OR) 2.61, 95 % confidence interval (95%CI): 1.51-4.51,p = 0.001], younger age (OR: 0.96, 95%CI: 0.95-0.97,p G 0.001), multifocality (OR: 2.20, 95%CI: 1.61-3.00,p G 0.001) and multicentricity (OR: 12.66, 95%CI: 6.82-23.49,p G 0.001), advanced clinical tumor stage (OR: 14.54, 95%CI: 5.80-36.47,p G 0.001), and baseline axillary nodal involvement (OR: 1.56, 95%CI: 1.12-2.17,p = 0.009). Comparison between groups did not show a significant difference in LRFS (p = 0.389). Conclusion: Many BC patients undergo mastectomy despite achieving complete response of primary tumor after NAT. Patients-related and tumor-related features, as well as having surgery in more recent years, seems to influence this choice. Our findings suggest the need for an optimized decision-making to spare unnecessary mastectomies.