Prevalence of drugs used for chronic conditions after diagnosis of thyroid cancer: a register-based cohort study.

Objective: Little is known about thyroid cancer survivors' risk of chronic conditions. We, therefore, investigated the prevalence of drugs used for chronic conditions among thyroid cancer patients using population-wide register data.

Methods: We linked data from the Cancer Registry of Norway to the Norwegian Prescription Database and other databases for a study population of 3.52 million individuals, including 3486 individuals with thyroid cancer diagnosed during 2005-2019. Prevalence ratios (PRs) with 95% CIs of reimbursed prescribed drugs in thyroid cancer patients up to 15 years after thyroid cancer diagnosis were estimated by log-binomial regression, with the cancer-free population as reference.

Results: Individuals (both males and females) with thyroid cancer had higher use of drugs for several chronic conditions in the years after diagnosis; eg, 5 years after thyroid cancer diagnosis, there was elevated use of drugs for hypoparathyroidism (PRmales = 35.4, 95% CI, 25.2-49.7; PRfemales = 42.8, 95% CI, 34.2-53.6), hypertension (PRfemales = 1.20, 95% CI, 1.12-1.28), anxiety and tension (PRmales = 4.01, 95% CI, 1.80-8.92; PRfemales = 2.01, 95% CI, 1.15-3.52), gastric acid disorders (PRmales = 1.52, 95% CI, 1.22-1.91; PRfemales = 1.45, 95% CI, 1.27-1.66), and pain (PRmales = 1.48, 95% CI, 1.11-1.97; PRfemales = 1.24, 95% CI, 1.08-1.42) as compared with the cancer-free population. In addition, males with thyroid cancer had long-term elevated use of drugs for depression (eg, year 10+, PRmales = 1.66, 95% CI, 1.06-2.59). Individuals with thyroid cancer also had higher use of drugs for several conditions prior to the thyroid cancer diagnosis, eg, hypertension, gastric acid disorders, and pain.

Conclusions: Individuals diagnosed with thyroid cancer had elevated long-term use of drugs for several chronic conditions, as compared with the cancer-free population.