278P - Correlation between radiologic complete response (rCR) in contrast-enhanced magnetic resonance imaging (CE-MRI) after neoadjuvant chemotherapy for early breast cancer and pathologic complete response and their impact in recurrence-free survival

Abstract

BackgroundPatients with early breast cancer (EBC) achieving pathologic complete response (pCR) after neoadjuvant chemotherapy (NACT) have a favorable prognosis. Breast surgery and more chemotherapy treatment might be avoided in patients in whom the presence of residual tumor can be ruled out with high confidence. We investigated the diagnostic accuracy of contrast enhanced MRI (CE-MRI) in predicting pCR and long-term outcome after NACT. MethodsPatients with EBC, who had undergone CE-MRI before and after NACT, were retrospectively analyzed (n=421), and regarding to the absence (radiologic complete remission; rCR) or presence (no-rCR) of residual contrast enhancement. ResultsOverall rCR and pCR rates were 35% (147/421) and 36% (154/421), respectively. We found a total of 70% (101/144) of rCR corresponded to a pCR (meaning the positive predictive value - PPV). In contrast, in 80% (219/272) of patients, residual tumor observed on MRI was pathologically confirmed (meaning the negative predictive value - NPV). Sensitivity to detect a pCR was 65% (101/154), while specificity to detect residual tumor and accuracy were 83% (219/262); and 76% (320/421), respectively. The PPV was significantly lower in luminal compared to HER2 positive and triple negative tumors (10/34 = 29 % vs. 50/62 = 81% and 41/48 = 85% respectively). The concordance between rCR and pCR was moderate (Cohen’s kappa − 0.5) but with low level in luminal tumors (Coheńs Kappa – 0.3). In multivariate analysis both assessments were significantly associated with disease free survival (rCR : HR:0,344 P=0.001; pCR : HR : 0,154 P=0.000), but not in luminal tumors (rCR : HR:0,813 P=0.692; pCR : HR : 0,326 P=0.275). ConclusionsThe accuracy of preoperative CE-MRI to predict pCR after NACT for EBC is moderate but in luminal tumors did not accurately predict pCR. However, rCR was strongly associated with favorable RFS, especially in HER2 positive and triple negative breast cancer tumors. Legal entity responsible for the studyThe authors. FundingHas not received any funding. DisclosureAll authors have declared no conflicts of interest.