Analyzing the Survival of Patients with Breast Cancer with a Multistate Model

Introduction: Breast cancer is the second most common cancer and one of the most common causes of death in women. Metastasis is also a challenge for breast cancer patients, affecting their survival. This study aimed to determine the survival rate and measure the factors affecting the progression of the disease from the time of diagnosis by considering metastasis as an intermediate condition using the disease-mortality model. Methods: This retrospective study included 493 women with breast cancer referred to Imam Khomeini Clinic, Hamadan, between 2001 and 2017. First, the required information was extracted from patients’ files according to a checklist, and then the effect of background and clinical variables on the natural course of the disease was examined using a multistate model. Results: The risk of metastasis for people whose tumor size was 2-5 cm and >5 cm was higher than that for people whose tumor size was <2 cm (HR, 1.28; [95% CI, 1.10-1.79]; and HR, 2.48; [95% CI, 1.25-3.91], respectively). People with estrogen-, progesterone-, and epidermal growth factor–positive tumors were at higher risk for metastasis (HR, 2.58; [95% CI, 1.96-3.40]; HR, 1.69; [95% CI, 1.7-2.26]; and HR, 1.73; [95% CI, 1.29-2.31], respectively). Conclusion: Public education on the importance of periodic examinations and early detection of breast cancer, as well as recognizing the symptoms of the disease, can help a person detect the disease early. Therefore, the patient can see a doctor before the tumor gets bigger and the disease progresses, which will help in timely treatment of the disease.