Temporal patterns of chronic disease incidence after breast cancer: a nationwide population-based cohort study

We conducted a retrospective cohort study to evaluate the temporal pattern of incidence of chronic conditions after developing breast cancer using a population-based national registry. We selected 84,969 women with newly diagnosed breast cancer between 2002 and 2016 and a 1:10 sample of age-matched non-breast cancer controls (N = 1,057,674). The main study exposure was incident breast cancer, considered as a time-varying exposure. The outcomes were incident cases of leukemia, endometrial cancer, myeloma, cardiomyopathy, osteoporosis, end stage renal disease (ESRD), pulmonary fibrosis, hypothyroidism, type 2 diabetes, hypertension and hyperlipidemia. The development of breast cancer was associated with a significantly increased risk of all outcomes analyzed except for ESRD and hypertension. The fully-adjusted risks of leukemia (HR 3.09; 95% CI 2.11-4.51), cardiomyopathy (HR 2.65; 95% CI 1.90-3.68), endometrial cancer (HR 3.53; 95% CI 2.76-4.53), hypothyroidism (HR 1.29; 95% CI 1.19-1.40), pulmonary fibrosis (HR 1.84; 95% CI 1.12-3.02), and hyperlipidemia (HR 1.24; 95% CI 1.20-1.28) remained significantly elevated after more than 5 years since diagnosis. Optimal care for breast cancer survivors requires close collaboration between oncologists and allied health care professionals to identify and manage the long-term morbidity and mortality associated with these chronic conditions.