Development and validation of a nomogram predicting pathologic complete response to neoadjuvant chemotherapy in luminal type breast cancer patients using MammaPrint® and clinicopathological factor

Purpose Pathological complete response (pCR) of neoadjuvant chemotherapy (NACT) is the most important predictor of successful treatment in locally advanced breast cancer and is associated with survival outcomes. The aim of our study is to investigate a validated nomogram that predicted MammaPrint® to assess the response rate in luminal type breast cancer. Methods This study retrospectively included patients from Asan Medical Center, Seoul, South Korea who were diagnosed with luminal type breast cancer and received NACT and underwent breast cancer surgery from August 2008 to December 2021. We used a nomogram previously published by colleagues at our center, using a cutoff score of 183. The primary outcome of this study was to investigate the use of nomogram adopted from a 70-gene MammaPrint for prediction of pCR following NACT. Results Data from 1,574 patients were collected. The nomogram using MammaPrint predicted pCR (odds ratio 2.092, 95% confidence interval 1.507–2.905; p < 0.001). Based on multivariate logistic regression analysis, estrogen receptor status, progesterone receptor status, clinical tumor stage, clinical node stage, and Ki67 index were independent predictive factors of pCR in the primary cohort. The area under the curve of the validated nomogram was 0.64 (95% confidence interval, 0.60–0.67), indicating the nomogram predicted pCR in the neoadjuvant setting. Conclusion This study provides evidence that the adopted nomogram using the MammaPrint risk assessment based on clinicopathological pre-NACT factors can be utilized in luminal type breast cancer to aid in treatment decisions.