The authors wrote, “Population-based studies that examine the associations between hyperthyroidism and cancer risk have yielded inconsistent results. It remains unclear whether the risks of different cancers increase in patients with Graves’ disease (GD) who received antithyroid drugs (ATDs) as initial treatment.”
The objective of the study was to ascertain whether cancer risk expands in patients with GD compared with controls.
For this nationwide retrospective cohort study, researchers employed data from the National Health Information Database of South Korea and included data from 29,502 patients aged >20 years with GD who received ATDs as initial treatment for more than 60 days from 2005 to 2012.
Adults with GD were matched 1:2 by age, gender, and index year, with a control group of 57,173 adults without GD, and incidences of cancer were obtained from diagnosis codes.
The primary outcome was defined as the incidence of various types of cancers, and hazard ratios (HRs) with CIs for cancer risk were assessed using Cox proportional hazards models. Accounting for the surveillance effect, the research also evaluated HR by follow-up period since the diagnosis of GD.
The results revealed the risk of developing biliary tract and pancreatic cancers were observed as (HR, 1.41; CI 1.24-1.60), thyroid cancer (HR, 15.51; CI, 12.29-19.57), prostate cancer (HR, 1.48; CI, 1.28-1.71), and ovarian cancer (HR, 1.31; CI, 1.13-1.52) was elevated in the GD group than in the control group even after the first year of follow-up was excluded.
The researchers also noted that the elevated cancer risks endured for over 5 years, particularly the risk of thyroid cancer in GD patients, which was notably higher during the initial follow-up period (1 to <2 years; HR, 19.35; CI, 7.66-48.87) compared with the period beyond 2 years. Moreover, the cancer risk estimates continued to be noteworthy even after eliminating GD patients who received radioactive iodine therapy.
Based on their findings, the authors concluded, “In this large-scale population-based study, GD was associated with increased risks of the biliary tract and pancreatic, prostate, ovarian, and thyroid cancers. The increased risk of thyroid cancer, particularly during the initial follow-up period, maybe a surveillance effect.”
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