Survival Analysis of Infiltrating Ductal Breast Cancer Patients with Cure Rate Regression Model- A Retrospective Cohort Study from a Tertiary Care Hospital in Central Kerala

Abstract

Introduction: Breast cancer is a leading cause of morbidity among women all around the world. Monitoring the survival pattern and identifying the prognostic factors on survival are always great concerns in cancer researches. Cure rate regression model is a useful statistical tool to predict the cure rate of cancer diseases and to determine the factors associated with survival of patients. Aim: The current study aimed to estimate the cured proportion and to make out the factors associated with survival time of infiltrating ductal breast carcinoma patients in a tertiary care hospital of central Kerala. Materials and Methods: The retrospective cohort study was conducted in the Department of Radiotherapy of a major tertiary care hospital of central part of Kerala, India. A total of 313 female patients diagnosed with infiltrating ductal breast cancer during January 2012 to December 2015 were considered for the study. The impact of the covariates, age at diagnosis of disease, grade of cancer, stage of disease, tumour stage, status of regional lymph node, distant metastasis, and triple negative status on survival of patients were studied. The parametric mixture cure rate regression model was used for estimation and inferential procedures. The cure rate with respect to each study variable and their role on long term survival of patients were investigated. Results: Mean age of patients was 51.95±10.91 years. The minimum cure rate found out (29.8%) among the patients presented with distant metastasis. The bivariate analysis showed the factors, stage of cancer, (T-stage), status of regional lymph node and distant metastasis status influence significantly on incidence of death due to breast cancer in long run period and grade of cancer determines the survival of patients at shorter duration of time. The presence of regional lymph node and distant metastasis status were found out to be two important indicators that determine cure rate of infiltrating ductal breast cancer patients in multivariate analysis. The hazard of patients living with higher grade cancer was seen 1.48 times more than that of others (Hazard Ratio=1.48, p-value <0.001). Conclusion: The cure rate of patients estimated between 29.8% and 69.6% with respect to various factors under study. The status of regional lymph node and distant metastasis status were found to be associated with cure rate of patients. The study results showed that the grade of cancer is one significant factor that determines survival of patients. The study recommends cure rate regression model as a useful tool to analyse breast cancer survival data in the presence of cured proportion.