Increased risk of breast cancer among premenopausal women with pituitary gland disorders in Taiwan: a population-based matched-cohort study.

Purpose: An association between pituitary gland disorders and breast cancer remains controversial. We examined the prevalence and risk of breast cancer over a 15-year follow-up period or until diagnosed as breast cancer among premenopausal women (12-49 years old) with pituitary gland disorders in Taiwan.

Methods: This retrospective matched-cohort study included 52,265 individuals each in the study group (women with pituitary gland disorders) and the matched control group from 2000 to 2004 identified using Taiwan's National Health Insurance Research Database. We compared sociodemographic characteristics and medical disorders between the two groups and examined the differences in clinicopathological characteristics of breast cancer. We also estimated the risk of breast cancer over 15 years of follow-up (median follow-up time = 11.2 years).

Results: Overall, 924 (1.8%) and 734 (1.4%) patients in the study and control groups, respectively, were diagnosed as having breast cancer (p < 0.001). Over the 15-year follow-up period, the study group had a 1.16-fold (95% confidence interval [CI] = 1.04-1.29, p < 0.05) increased risk of breast cancer compared with the control group. This risk was particularly pronounced in the 20-29 and 30-39 age groups (adjusted hazard ratio = 1.46 and 1.25, respectively; 95% CI = 1.15-1.86 and 1.07-1.44, p value < 0.01, respectively).

Conclusion: Our findings reveal a relationship between pituitary gland disorders and breast cancer among premenopausal women in an Asian country. Physicians should check for signs of breast cancer in premenopausal women with pituitary gland disorders for early detection and treatment. Future studies should confirm our findings and clarify the causal relationship.