Int J Cancer Manag. 2020 January; 13(1):e87176. Published online 2020 January 26. doi: 10.5812/ijcm.87176. Research Article Inverse Entezar Weibull and Its Application in Identification of Influential Factors on the Survival of Patients with Blood Cancers Nazanin Ramezani 1 , Naghmeh Khadembashi 2 , Sina Salari 3 , Abbas Hajifathali 3 , Mostafa Faridizadeh 1 and Ahmad Reza Baghestani 4, * 1 Department of Biostatistics, Faculty of Paramedical Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran 2 English Language Department, School of Allied Medical Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran 3 Hematopoietic Stem Cell Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran 4 Department of Biostatistics, Physiotherapy Research Center, Faculty of Paramedical Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran * Corresponding author: Department of Biostatistics, Physiotherapy Research Center, Faculty of Paramedical Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Tel: +98-2122707347, Email: baghestani.ar@gmail.com Received 2018 December 08; Revised 2019 October 17; Accepted 2019 October 26. Abstract Background: Blood cancer is a disease with a high burden level and a mortality rate of 2.8% which has a growing trend in Iran. For this reason, it is important to study the survival ratio of patients who were afflicted with this disease. The present study was conducted to determine the factors affecting the survival time of patients with various types of blood cancers. Objectives: This is a historical cohort study that examines the survival of patients with blood cancer who received bone marrow transplants in the presence of some explanatory variables. Methods: This descriptive-analytical study was performed on data extracted from files in the bone marrow transplant department, Taleghani Hospital, Tehran, Iran which is affiliated with Shahid Beheshti University of Medical Sciences. Patients who were candi- dates for a bone marrow transplant from all over the country (from 2007 to 2016) with different types of complaints were considered as the subjects of this study. Inverse Entezar Weibull model was used to analyze the survival time and investigate the factors affecting the survival of patients. Results: Of 99 patients, 20.1% died of a type of blood cancer. One-year, five-year and eight-year survival of patients were 90.2%, 76.6%, and 74.2%, respectively. Age at diagnosis time, number of relapses before bone marrow transplant, and the type of diagnosis were identified as factors affecting the survival time of patients with different types of blood cancer. Conclusions: This study showed that age factor at the time of diagnosis, the number of relapses before the bone marrow transplant, and the type of diagnosis were effective factors in the survival of patients with blood cancer. Keywords: Blood Cancers, Survival Analysis, Inverse Entezar Weibull Model, Survival Time 1. Background According to the World Health Organization (WHO) re- port, more than 25 million people in the world are cur- rently living with cance. More than 18.1 million people get afflicted with this disease, and about 9.6 million die of it. Cancer is the third leading cause of death in Iran. According to the National Comprehensive Cancer Control Program (NCCCP) report, it is estimated that more than 80000 new cases of cancer occur annually in the country, and more than 30000 die out of the disease in Iran (1-3). Cancer is referred to as the unbridled process of cell di- vision. Blood cancers affect the production and function of blood cells. Most of these cancers begin in the bone mar- row where blood is manufactured. Stem cells mature in the bone marrow and develop into three groups of red blood cells (RBCs), white blood cells (WBCs) and platelets (PLTs). In most blood cancers, the normal stages of devel- opment of blood cells are impaired by the uncontrolled growth of abnormal blood cells. Cancer cells inhibit many of the blood functions such as fighting infections and pre- venting severe bleeding. All in all, the blood cancers are caused by the impairment in the production and matura- tion of white blood cells (4-7). Survival analysis is a collection of statistical methods for analyzing the study data at a specific time until the oc- currence of the event (8). This branch of statistics is widely used nowadays in various disciplines, including medicine. The unique survival analysis feature is the use of censored data in analysis processes. “Censored” means that some participants of the study may not experience the event- Copyright © 2020, Author(s). 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