A comprehensive nationwide registry study of noncommunicable disease comorbidities and death in cancer patients in Norway-the NCDNOR project.

Noncommunicable disease (NCD) comorbidities are common in cancer patients due to shared risk factors, but few studies have mapped their occurrence across cancer types using detailed national data. In this nationwide cohort study, we used data from Norwegian mandatory health registries to comprehensively describe NCD comorbidities at and after cancer diagnosis of 19 cancers. We included 269,956 adults registered with a first cancer in the Cancer Registry of Norway 2009-2019. Comorbidities included second cancers, cardiovascular diseases (CVDs), chronic obstructive pulmonary disease, diabetes and mental health disorders (MDs). We used intersection diagrams to examine NCD comorbidity patterns at first cancer diagnosis, and multi-state models to estimate five-year post-cancer probabilities of NCD comorbidities and death. We also provide a publicly available online application [ https://ncdapp.onrender.com/ ] with additional results and details. Comorbidity prevalence at cancer diagnosis ranged from 35% (skin cancer) to 83% (lung cancer). CVD was most prevalent, usually co-occurring with MDs or diabetes. Lowest prevalences were found for younger patients and women. Conditioning on surviving five years, comorbidity probability exceeded 50% in all sites. Our findings show substantial comorbidity burden in cancer patients, varying by cancer site, age, and sex. Knowledge of these patterns could improve NCD prevention, treatment and surveillance.