Development and External Validation of a Clinical Nomogram for Individually Predicting Survival of Metaplastic Breast Cancer

Background: Few studies have concerned the prognosis of metaplastic breast cancer (MpBC), a rare and diverse malignancy. A prognostic index estimating the MpBC survival would be attractive in clinical practice. Patients and Methods: We retrospectively analyzed MpBC patients from the Surveillance, Epidemiology, and End Results (SEER) database. Prognostic factors were identified and the final nomogram was developed to predict the 1-, 3-, or 5-year overall survival (OS). Calibration curves were provided to internally validate the performance of the nomogram and discriminative ability was appraised by concordance index (C-index). Results: A total of 1017 MpBC patients diagnosed between 2010 and 2015 were assigned into 3:1 as training set (n = 763) and SEER validation set (n = 254). An external validation was performed by an individual set of 94 MpBC patients from National Cancer Center in China from 2010 to 2018. The nomogram finally consisted of 7 independent prognostic factors and presented a good accuracy for predicting the OS with the C-index of 0.77 (95% CI: 0.751-0.786). Interestingly, the nomogram based on the western (including 92.5% non-Asian) SEER validation population (C-index of nomogram: 0.76, 95% CI: 0.737-0.796) also has an optimal discrimination in Asian population (C-index of nomogram: 0.70). The calibration plots of the nomogram predictions were also accurate and corresponded closely with the actual survival rates. Conclusion: This novel nomogram was accurate enough to predict the OS by using readily available clinicopathologic factors in MpBC general population, which could provide individualized recommendations for patients and clinical decisions for physicians.