Do patients whose tumor achieved a pathological response relapse at specific sites? A substudy of the EORTC 10994/BIG-1-00 trial

Purpose To determine the sites of first distant relapse in patients with or without pCR following neoadjuvant chemotherapy in breast cancer patients enrolled in the EORTC 10994/BIG-1-00 trial. Methods We included patients enrolled in the EORTC 10994/BIG-1-00 trial who received at least one chemotherapy cycle before surgery and who had been diagnosed with a distant relapse. pCR was defined as no evidence of residual invasive cancer in the primary tumor and axillary lymph nodes with or without residual ductal carcinoma in situ. Site of first distant relapse was categorized as 'soft tissue,' 'visceral,' 'skeletal,' 'central nervous system (CNS),' and 'other.' The association between relapse site and achievement of pCR was assessed using multivariate logistic regression models for molecular subtypes classification and preceding locoregional recurrence. Results The study included 383 (21%) eligible patients out of the 1856 randomized, of whom 28 (7%) had achieved pCR. Median follow-up was 5.4 years. Achievement of pCR was associated with a trend towards a decreased presentation of skeletal metastases [21% (pCR) vs. 50% (non-pCR), OR 0.32, adjusted p value = 0.071] and an increase in the proportion of patients with CNS metastases as first distant relapse site (21% vs. 9%, OR 2.39, adjusted p value = 0.183). Patients with pCR were more likely to present with only one relapse location category when compared to non-pCR (86% vs. 69%). Conclusion Patients that achieved a pCR appeared less likely to present with skeletal metastases and more frequently presented with CNS metastases as first site of distant relapse, even after adjustment for molecular subtypes.