Diagnostic Correlates of Tumor Biology and Immediate Breast Reconstruction After Mastectomy: Real-World Evidence from a Romanian Cohort.

Background/Objectives: Tumor biology-particularly HER2 expression, Ki-67 proliferation index, and triple-negative phenotype-has traditionally influenced the timing of breast reconstruction after mastectomy. However, real-world data from Eastern Europe remain limited, and variability in access and clinical practice persists. This study aimed to determine whether tumor biology independently predicts the likelihood of immediate breast reconstruction (IBR) in a multidisciplinary tertiary center. Methods: We performed a retrospective cross-sectional analysis of 208 consecutive patients who underwent mastectomy with or without IBR between January 2023 and January 2024. Associations between tumor biology (HER2 status, Ki-67 index, and triple-negative subtype) and IBR were examined using χ2 tests, independent samples t-tests, and multivariate logistic regression adjusting for age, BMI, smoking status, comorbidities, neoadjuvant chemotherapy, pathological tumor size (pT), nodal stage (pN), and surgery type. Statistical significance was set at p < 0.05. Results: IBR was performed in 41.4% of HER2-positive and 41.2% of HER2-negative patients (p = 1.00). Reconstruction rates across Ki-67 quartiles (≤10%, 11-20%, 21-40%, ≥41%) were 50.0%, 37.5%, 34.4%, and 37.5%, respectively (p = 0.58). Triple-negative status was not associated with IBR in multivariate analysis (OR = 0.44, 95% CI 0.08-2.18, p = 0.32). Significant predictors of IBR included younger age (OR = 0.87, 95% CI 0.80-0.93, p < 0.001) and less extensive surgery (OR = 0.23, 95% CI 0.09-0.59, p = 0.002). The mean interval to adjuvant therapy was comparable between IBR (28.7 ± 6.2 days) and non-IBR (27.9 ± 5.8 days) groups (p = 0.34), indicating that reconstruction did not delay systemic treatment. Conclusions: In this real-world Romanian cohort, tumor biology did not significantly influence immediate reconstruction decisions. Age and surgical extent were the main determinants of IBR, suggesting that reconstructive access was guided more by clinical than molecular factors. These findings support the shift toward multidisciplinary, biology-informed, and patient-centered surgical decision-making, in line with current ESMO and NCCN recommendations. Despite limitations-including the retrospective design, single-center setting, incomplete BRCA data, and absence of long-term oncologic outcomes-the study provides novel regional perioperative evidence supporting safe and equitable access to immediate reconstruction across biologic subtypes.