Nomogram to predict pathologic complete response in HER2-positive breast cancer treated with neoadjuvant systemic therapy

Background:Pathologic complete response (pCR) is associated with improved survival outcomes in patients with HER2-positive primary breast cancer. We developed a nomogram to predict the probability of pCR rates by using oestrogen receptor (ER) expression, progesterone receptor (PR) expression and HER2/CEP17 ratio as continuous variables.Methods:We retrospectively reviewed patients with stages I-III HER2-positive invasive breast cancer who had definitive surgery in 1999-2015 and received neoadjuvant systemic therapy (NST). Multivariate logistic regression models were applied to assess the effect of variables on pCR. A nomogram was built to estimate the probability of pCR. The discriminative ability was estimated by the concordance index (C-index). The accuracy was assessed graphically with a calibration curve.Results:A total of 793 patients were included in the analysis. Low ER expression (P<0.001), high HER2/CEP12 ratio (P=0.03), and non-inflammatory breast cancer subtype (P=0.003) were associated with increased pCR rates. Regimens containing trastuzumab or trastuzumab and pertuzumab were associated with higher pCR rates than cytotoxic agents alone (P<0.001 and P<0.001, respectively). The C-index was 0.69. The calibration curve showed good agreement.Conclusions:Our nomogram predicted the pCR rate after NST among patients with HER2-positive primary breast cancer using clinicopathologic factors.