Assessing the malignancy rate of adrenal nodules in patients with a history of cancer: factors associated with adrenal metastases.

[OBJECTIVES] To determine malignancy rate of adrenal nodules in patients with a history of cancer and identify factors predictive of adrenal metastases.

[METHODS] This Institutional Review Board-approved, retrospective study was performed 1/1/2010-12/31/2020 at an academic health system. Cancer registry data and natural language processing identified patients with a history of extra-adrenal malignancy who had undergone contrast-enhanced abdominal CT or MRI and had adrenal nodules ≥ 1 cm. A power calculation based on previously published prevalence of malignancy in adrenal nodules determined the minimum number of patients. The reference standard used for diagnosis was pathology when available, or imaging follow-up ≥ 1 year. Cancer type, presence/absence of extra-adrenal metastatic disease on index scan, and size of the adrenal nodule were extracted from the electronic health record. These factors were correlated with adrenal nodule outcome (benign or metastatic) using univariate and multivariable logistic regression analyses.

[RESULTS] The cohort included 420 patients (219 female; mean age 71.4 years [standard deviation 11.1]). Overall metastatic adrenal nodule rate was 15.7% (66/420). Patients with extra-adrenal metastatic disease were more likely to have metastatic adrenal nodules compared to those with an isolated adrenal nodule (24.5% [37/151] vs. 10.8% [29/269]; p ≤ 0.001). Adrenal metastases were most common in patients with melanoma (50%, 10/20) and lung cancer (32%, 24/75). Metastatic rate increased with nodule size 2-4 cm (Odds Ratio [OR] 1.98) and > 4 cm (OR 3.25). In patients with an isolated adrenal nodule, primary malignancy (lung cancer: OR 10.80; melanoma: OR 32.91) and size (2-4 cm: OR 5.14, > 4 cm: OR 9.69) were associated with increased risk of metastases.

[CONCLUSION] In a cohort of patients with a history of any type of malignancy, almost 90% of isolated adrenal nodules were benign. However, a history of lung cancer, melanoma, or lesion size ≥ 2 cm significantly increased the risk of adrenal metastases.