Ultrasound-based prediction of pathologic response to neoadjuvant chemotherapy in breast cancer patients

Background Accuracy in predicting pathologic response to neoadjuvant chemotherapy (NACT) in breast cancer is essential for the determination of therapeutic efficacy and surgical planning. This study aimed to assess the precision of ultrasound (US) for predicting pathologic complete response (pCR = ypT0) after NACT. Methods This retrospective mono-center study included 124 invasive breast cancer patients treated with NACT. Patients received US before and after NACT with documentation of clinical partial response (cPR) and clinical complete response (cCR). Post-operatively, the pathologic response was defined as absence of tumor cells (ypT0), presence of non-invasive tumor cells (ypTis) or invasive tumor cells (ypTinv). Sensitivity and specificity of US as well as false negative rate (FNR), negative predictive value (NPV) and positive predictive value (PPV) were analysed for receptor subtypes. A multivariable logistic regression model assessed the influence of patient- and tumor-associated covariates as predictors for pCR. Results 50 patients (40.3%) achieved pCR, 39 (78.0%) had a corresponding cCR. Overall sensitivity was 60.8% and specificity 78.0% for US-predicted remission. NPV and FNR differed substantially between subtypes. NPV was highest (75.0%) in triple negative (TN) subtype, while FNR was low (37.5%). Therefore, pathological response was most accurately predicted for TN cancers. NPV for human-epidermal-growth-factor-receptor-2-positive/hormone-receptor-positive (HER2+/HR+) was 55.6%, for HER2+/HR- 64.3% and for HER2-/HR+ 16.7%, FNRs were 40.0%, 71.4% and 32.3%, respectively. Receptor subtypes impacted pCR significantly (p-value: 0.0033), cCR correlated positively with pCR (p-value: 0.0026). Conclusion US imaging is insufficient to predict pCR with adequate accuracy. Receptor subtypes, however, affect diagnostic precision of US and pathologic outcome.