Contribution Factors on Long- term and Short- term Survival of Thalassemia Major Patients

Thalassemia major is an important health problem in Mediterranean countries, placing a tremendous emotional, psychological, and economic burden. This study aimed to evaluate the effective factors on long- and short-term survival of thalassemia major patients using mixture and non-mixture cure survival models based on generalized-Gompertz distribution. The generalized-Gompertz distribution has flexible curve of failure rate that may be appropriate for different situation of survival analysis.

In this retrospective cohort study, medical records of 300 thalassemia major patients referring to Zafar's thalassemia clinic during 1994-2017 in Tehran, Iran were reviewed. Mixture and non-mixture cure survival models based on Gompertz and generalized-Gompertz distributions were performed to investigate the survival of thalassemia major patients and the influential factors in their survival and longevity. The Akaike Information Criteria was used to compare the models. Analysis was performed using SAS software version 9.4.

The mean survival time was 32.21 ± 7.47years. The censorship rate was 78.3%. In both of the mixture and non-mixture cure models, generalized Gompertz distribution, as compared to the standard Gompertz had the lower Akaike (AIC) criteria that was 200.8. Based on this model, iron deposition in liver at mild and moderate levels had a significant effect on the long-term survival of these patients.

Based on Akaike Information criteria, considering the generalized Gompertz mixture cure model has the best fit for the data of thalassemia major disease in which patients are long-term survivors. In order to analyze the survival of patients with thalassemia major, since iron deposition in liver at mild and moderate levels had a significant effect on the long-term survival of these patients; it is recommended to regular iron chelation therapy for extra iron extraction.