Use of drugs for chronic diseases in female breast cancer survivors: a nationwide cohort study

Background Breast cancer survivors experience health consequences of the disease and its treatment. This study evaluated the incidence of drug use as a proxy for chronic diseases in breast cancer survivors. Methods Data from Cancer Registry of Norway was linked to Norwegian Prescription Database and other national registries for a study population of 1.76 million women born during 1920–90, including 39,039 women diagnosed with breast cancer during 2005–19. Hazard ratios (HRs), with 95% confidence intervals (CIs), of dispensed drugs for chronic diseases in breast cancer patients up to 15 years after diagnosis were estimated using Cox regression with cancer-free women as reference. Results Five years after diagnosis, 55% of breast cancer patients used at least one of the examined drugs for chronic diseases compared with 48% of the cancer-free women. The overall HR was highest for drugs used for anxiety and tension (HR 12.4; CI 11.9–12.8) and for steroid-responsive conditions (9.54; 9.32–9.76), and the HRs were especially high the first years (0–2 years) after diagnosis. The breast cancer patients also used drugs for cardiovascular diseases (CVDs) more often (overall 1.81; 1.77–1.86), except drugs for coronary heart disease (0.75; 0.70–0.81). Overall, the drug use was higher in patients with late-stage disease and in women below 55 years at diagnosis. Conclusions Breast cancer survivors had higher use of medications for chronic diseases, particularly for anxiety and tension, and steroid-responsive conditions, but also for CVDs, the first years after diagnosis—most prominently in those with late-stage disease and in younger women.