Non-cancer risks among female breast cancer survivors: a matched cohort study in Japan

Background: The number of breast cancer (BC) survivors has increased worldwide, but the landscape of their non-cancer disease risks remains unclear, especially among Asian women. Methods: In the JMDC claims database, which covers company employees and their family members in Japan, women aged 18-74 years with and without an incident BC were matched in a 1:4 ratio for age and entry timing to the database between January 2005 and December 2019. The risks for six cardiovascular diseases (myocardial infarction, heart failure, atrial fibrillation/flutter, ischaemic stroke, intracranial haemorrhage, and pulmonary embolism) and six non-cardiovascular diseases (major osteoporotic fractures, other fractures, gastrointestinal bleeding, urinary tract infection, infectious pneumonia, and anxiety/depression) were compared between the groups. Findings: Comparing 24,017 BC survivors and 96,068 matched women (mean age, 50.5 years, standard deviation, 8.7 years), the incidence rates of heart failure, atrial fibrillation/flutter, and all non-cardiovascular diseases were higher in the BC survivor group. The highest adjusted hazard ratio (HR) was noted for heart failure (3.99 [95% confidence interval 2.58-6.16]), followed by gastrointestinal bleeding (3.55 [3.10-4.06]), and anxiety/depression (3.06 [2.86-3.28]). The HRs in the first year were larger than those for 1-10 years for most outcomes, whereas the HRs for fracture outcomes were larger for 1-10 years. Interpretation: BC survivors in Japan showed an increased risk of many non-cancer diseases compared to women without BC. Most risks increased more steeply during the first year following diagnosis, whereas the risk of fractures increased later. Funding: Competitive research funding from Pfizer Health Research Foundation in Japan.