MRI response to neoadjuvant chemotherapy and prognostic implications in breast cancer patients

OBJECTIVE: To correlate response evaluation after neoadjuvant chemotherapy (NAC), assessed by MRI and pathology, with disease-free survival (DFS) in breast cancer patients, according to immunophenotype. METHODS: Single-centre, IRB-approved retrospective cohort study included consecutive breast cancer patients who underwent NAC and preoperative breast MRI. Pathologic response was evaluated using the residual cancer burden (RCB) system, with pathological complete response (pCR) defined as the absence of invasive carcinoma. Radiological complete response (rCR) was defined as the absence of abnormal enhancement on MRI. The Kaplan-Meier method estimated DFS and Cox regression analysis calculated hazard ratios (HRs). RESULTS: Five hundred seventy-one patients were included (mean age 46 years, range 26-90). The most common immunophenotype was luminal (42.3%), followed by triple-negative (TNBC, 31.5%) and HER2 overexpressed (26.3%). Radiological and pathological responses were concordant in 71.5%. Overall, 35.2% achieved rCR and 37.5% achieved pCR. Disease-free survival curves did not differ significantly according to radiologic-pathologic response combinations in the luminal or HER2 groups (LogRank P = .505 and P = .257). In the TNBC group, patients without pCR or rCR had significantly worse DFS compared to those achieving either response (LogRank P = .001). Cox regression revealed that TNBC patients with both non-rCR and non-pCR had a markedly higher risk of recurrence or death (HR 7.728; 95% CI 2.696-22.149; P < .001). CONCLUSIONS: Integrating MRI and pathological response assessments after NAC may enhance risk stratification and prognostication, especially in triple-negative breast cancer. ADVANCES IN KNOWLEDGE: Patients with both non-rCR and non-pCR have significantly worse DFS, underscoring the prognostic value of combining imaging and pathological findings, particularly in TNBC.