Predictive models for overall survival in breast cancer patients with a second primary malignancy: a real-world study in Shanghai, China

Background The incidents of second primary malignancy (SPM) is increasing among breast cancer (BC) patients with long-term progression, adversely affecting survival. The purpose of this study was to screen independent overall survival (OS) risk factors and establish nomograms to predict the survival probabilities of BC patients with SPM. Method A total of 163 BC patients with SPM were recruited during 2002–2015 from a total of 50 hospitals in Shanghai, China. Two nomograms to predict survival from primary BC and SPM diagnosis were constructed based on independent factors screened from multivariable analysis. The calibration and discrimination of nomograms were calculated in the training and validation cohorts. Results The overall survival rates of BC patients with SPM were 88.34%, 64.42% and 54.66% at 5, 10 and 15 years, respectively. Factors of late TNM stage of SPM (HR = 4.68, 95% CI 2.14–10.25), surgery for SPM (HR = 0.60, 95% CI 0.36–1.00), SPM in the colon and rectum (HR = 0.49, 95% CI 0.25–0.98) and thyroid (HR = 0.08, 95% CI 0.01–0.61) independently affected the OS of BC patients with SPM ( p < 0.05). In addition, a longer latency (≥ 5 years) was associated with better OS from BC diagnosis ( p < 0.001). Older age (≥ 56) was associated with poor OS from SPM diagnosis ( p = 0.019). Two nomograms established based on the above factors had better calibration and discrimination. Conclusion The TNM stage of SPM, surgery for SPM, SPM sites, latency and age at BC diagnosis are independent factors for survival and the two nomograms may provide more personalized management for BC patients with SPM.