The Incidence of Cancers in Patients With Nonfunctional Adrenal Tumors: A Swedish Population-Based National Cohort Study.

Context: It is unclear if nonfunctional adrenal tumors (NFAT) are associated with higher cancer incidence. Objective: To analyze the cancer incidence in patients with NFAT. Methods: In this national register-based retrospective cohort study, consecutive patients with NFAT identified in Sweden 2005-2019 and matched control individuals without adrenal tumors were followed up to 15 years. Outcome data were collected from national registers and adjusted for confounders. Both cases and controls were followed until newly diagnosed malignancy, death, or until 2019. Individuals with adrenal hormonal excess or prior malignancy were excluded. Results: Among 17 726 cases, 10 777 (60.8%) were women, and the median age was 65 (IQR, 57-73) years. Among 124 366 controls, 69 514 (55.9%) were women, and the median age was 66 (IQR, 58-73) years. The incidence of any cancer was higher in patients with NFAT compared to controls (hazard ratio [HR] 1.35 95% CI 1.29-1.40; adjusted HR 1.31, 95% CI 1.26-1.37). NFAT was associated with a higher incidence of adrenal, thyroid, lung, stomach and small intestine, kidney, pancreatic, breast, and colorectal cancer. Sensitivity analyses did not change the overall results, but associations were not significantly increased after adjustment in patients with NFAT and appendicitis or gallbladder/biliary tract/pancreas disorders. Cancer incidence may have been underestimated by adjusting for unclear and benign tumors. Conclusion: The incidence of cancer was increased in patients with NFAT. Long-term follow-up may be indicated.