Increased breast cancer risk for patients with multiple sclerosis: a nationwide population-based cohort study.

BACKGROUND AND PURPOSE: Studies have suggested that multiple sclerosis (MS) might be linked to an overall reduced cancer rate, but a positive relationship is also found for several types of cancer. This study determines whether MS is associated with cancer risk in Taiwan.

METHODS

Data from the National Health Insurance System of Taiwan were used to assess this issue. The MS cohort included 1292 patients, and each patient was randomly frequency-matched with four participants without MS, based on their age, sex and index year (control cohort). Cox proportional hazards regression analysis was conducted to estimate the influence of MS on cancer risk.

RESULTS

A significantly higher risk of developing overall cancer was found amongst the MS cohort compared with the control cohort [adjusted hazard ratio (HR) 1.85, 95% confidence interval (CI) 1.26-2.74], as well as breast cancer (adjusted HR 2.23, 95% CI 1.11-4.46).

CONCLUSIONS

The nationwide population-based cohort study revealed that Taiwanese patients with MS have a higher risk of developing overall cancer types and breast cancer in particular.