Joint modeling of longitudinal change in tumor cell level and time to death of breast cancer patients: In case of Ayder comprehensive specialized Hospital Tigray, Ethiopia

Abstract Abstract: Breast cancer is the major public health problem throughout the world and it results in serious physical damages and death. This work proposes the use of joint model to study breast cancer in patients of Ayder Hospital. The primary motivation is to contribute to the understanding of the tumor cell progression of breast cancer, within Ayder Hospital, using a joint model that takes into account a possible existence of a serial correlation structure within a same subject observations from September 2015 till December 2018. The general aim of this study was to investigate the risk of longitudinal change in tumor cell level on time to death due to breast cancer among breast cancer patients. Hospital-based retrospective cohort study was conducted among breast cancer patients. A joint model of longitudinal and time to death model was used to determine the risk of longitudinal change in tumor cell level on time to death due to breast cancer patients. These were used by using JM package in R version. Results from joint models, showed that the longitudinal Tumor cell progression was signicantly associated with the survival probability of these patients(estimated association parameter(ɑ) in the joint model is 0.84 with corresponding (95% CI: 2.28,2.37). A comparison between parameter estimates obtained in this joint model and independent survival and longitudinal analysis lead us to conclude that independent analysis brings up bias parameter estimates. There is a strong association between the progression change in log(TCL) and risk of mortality due to breast cancer.