Simultaneous modeling of multiple recurrences in breast cancer patients

Introduction: Breast cancer is one of the most common recurrence cancers among women. There are several factors that can affect multiple recurrence of this disease. On the other hand, simultaneous examination of the types of relapses will make the results more accurate. The purpose of this study was to use a joint frailty model to model multiple recurrences of breast cancer patients. Materials and Methods: In this retrospective survival study,342 breast cancer patients whose records were registered at the Shohada Tajrish Hospital Cancer Research Center (Tehran, Iran) were investigated in 2005-2015. Patients were monitored for at least 6 months after diagnosis and their last condition was recorded in this study, the joint frailty survival model was used and data analysis was done in R software version 3.4.1. Results: The 3-year and 5-year survival rates were 0.79 and 0.68 respectively. According to the results of the fitted joint frailty model, it can be said that the risk of multiple recurrence is increased for patients with tumor grade greater than I. Also, tumor size (>20 mm) has a significant effect on the risk of recurrence and the risk of local and metastatic recurrence is more for HER2+ patients. Conclusion: According to the results of this study, the relationship between metastasis and local relapses was high in breast cancer patients, which has great importance in the process of recognizing and treating of this disease. Although in this study, in a large sample of patients, there was a positive correlation between multiple recurrences, but these results should be considered with caution with small number of recurrences.