Estimating short-term and long-term survival in rectal cancer patients using cure model.

Background: A large number of rectal cancer patients are cured after treatment. In such cases, cure models are used for survival analysis. This study aims to investigate factors that affect survival in rectal cancer using the Cox mixture cure model.

Methods: Following a retrospective design, medical documents and pathological findings of newly diagnosed rectal cancer cases hospitalized at Imam Hossein Hospital, Tehran, Iran, from 2005 to 2013 were reviewed. The patients were followed up with until May 2018. The Cox mixture cure model was used. Data analysis was carried out using Statistical Analysis System (SAS) version 9.4. The statistical significance level was considered to be 0.05.

Results: Four hundred nine patients were included in this study. The mean of disease-free survival was 87.08 ± 3.2 months. The hazard of the event for the patients who were drug abusers was 2.37 (95% CI: 1.30-4.31) times more than the other cases ( = 0.005). The odds ratio of the event for patients of stage III was 3.04 (95% CI: 1.51-6.12) times more than the cases of stage I ( = 0.002), and for the patients of stage IV, it was 12.42 (95% CI: 4.17-37.01) times more than patients of stage I ( < 0.001).

Conclusions: The results of this cure model indicate that the tumor stage, tumor grade, and history of drug abuse are the risk factors for the survival of patients with rectal cancer. These results can attract the attention of doctors and patients who want to be aware of their physical status and prognosis.