The Effects of Prognostic Factors on Metastasis and Survival of Patients with Breast Cancer Using a Multi-State Model

Background: The multi-state models help more closely study of the factors affecting the survival of patients with breast cancer. Method: We conducted the present retrospective cohort study on 2030 Iranian patients with breast cancer in 2020. The patients’ follow-up period ranged from 1 month to 15 years. Accordingly, the initial treatment, metastasis, and death were considered as the first, second, and absorbing states, respectively. The multi-state model was utilized for modeling and analyzing the data at a 95% significance level using the MSM package in R software. Results: The mean age (±SD) of the patients included at diagnosis time was 55.3 (±12.07) years old. The first one year and 5 years adjusted transition probabilities for transitions from the treatment to metastasis estimated as 0.85 (0.15 – 0.89) and 0.45 (0.21 – 0.61), and for metastasis to death transitions, they were estimated as 0.15 (0.1 – 0.21) and 0.55 (0.41 - 0.69), respectively. Moreover, the average sojourn times were estimated as 0.27 and 74.85 months for the treatment and metastasis states, respectively. Conclusion: The obtained results revealed that over time, the transition probabilities of patients from surgery to metastasis state decreased whereas the transition probabilities from metastasis to death state increased using the multi-state model.