DCE-MRI for assessment of pathologic complete response after completion of neoadjuvant therapy in triple-negative breast cancer patients.

611 Background: Triple-negative breast cancer (TNBC) is an aggressive molecular subtype that accounts for approximately 15%-20% of all breast cancer diagnoses. We aimed to investigate the utility of presurgical DCE breast MRI as a predictive marker for pathologic complete response (pCR) after neoadjuvant treatment (NAT) in TNBC patients and to compare the predictive value of early versus delayed enhancement for residual tumor detection. Methods: A total of 308 Stage I–III TNBC patients who underwent preoperative DCE-MRI after completion of NAT followed by surgery were enrolled in an IRB-approved prospective clinical trial (NCT02276433). Tumor size was measured using three-dimensional measurements of the index lesion during both the early (1 min) and delayed (6 min) phases of DCE-MRI. Treatment response at surgery (pCR vs. non-pCR) and the pathologic size of residual disease were documented. Correlation between pCR and residual enhancement on DCE-MRI was assessed using McNamar’s test. Spearman’s rank correlation coefficient was used to assess concordance between the longest diameter on MRI and pathology. Differences between longest diameter on DCE-MRI and pathology were compared using the Wilcoxon signed-rank test. Results: Among the 308 TNBC patients, 47% (145/308) achieved pCR following treatment. Residual disease detection on the early phase of DCE-MRI demonstrated higher sensitivity for predicting pCR compared to the delayed phase (79% vs. 69%, p < 0.001); however, it had lower specificity (78% vs. 84%, p = 0.008). Absence of enhancement in both early and delayed phase DCE-MRI predicted pCR with positive predictive values (PPV) of 80% and 83%, respectively. Residual enhancement in both phases predicted non-pCR with negative predictive values (NPV) of 77% and 71%, respectively. Both early and delayed DCE-MRI phases demonstrated a similar moderate positive correlation with pathology (r = 0.64 vs. 0.62). There was no significant difference between the longest diameter measured on early phase DCE-MRI and pathology (p = 0.706), whereas a significant difference was observed for the delayed phase (p < 0.001), which over estimated residual disease. Conclusions: Presurgical DCE-MRI demonstrated strong performance in predicting pCR among TNBC patients following NAT. The early and delayed phases of DCE-MRI may each capture different aspects of tumor characteristics, potentially providing complementary information for prediction. Clinical trial information: NCT02276433 .