A Case-Control Study of Breast Cancer in Northeast of Iran: The Golestan Cohort Study

The incidence and survival of breast cancer (BC) vary across countries. This study aimed to determine risk factors for BC and estimate the overall survival rate in BC patients of the Golestan Cohort Study (GCS). This case-control study was performed among participants of the GCS. Cases (N = 99) consisted of women who were diagnosed with BC and controls (n = 400) were selected out of women participating in the same cohort and had not developed any cancer during the follow-up period. Controls were frequency matched to case on both place of residency and 5-year categories of age. Considering confounding variables, logistic regression analysis manifested a reverse association between parity and BC (OR [odds ratio] = 0.87, 95% CI: 0.80–0.95, P = 0.001). In addition, we found women who had family history of any cancer (OR = 1.63, 95% CI: 1.02–2.60, P = 0.04) and long term oral contraceptive (OCP) use (≥10 years) (OR = 3.17, 95% CI: 1.27–7.95, P = 0.01) were at higher risk of BC. Of the total patients, 23 (23.2%) were died due to BC after a mean follow-up of 102.4 ± 5.31 months. Using the Kaplan-Meier analysis, the 5-year survival in these patients was 74%. In the Golestan Cohort population, long term OCP use and family history of cancer were risk factors for BC, while parity was a protective factor. The 5-year survival of BC patients in the GCS is still lower relative to Europe and the United States.