Adrenal Insufficiency following Stereotactic Ablative Radiotherapy (SAbR) of Adrenal Gland Metastases.

Simple Summary: Stereotactic ablative radiation (SAbR) is a focused, high-dose radiation technique used to treat cancers that have spread to the adrenal glands. One of the feared consequences of this therapy is causing adrenal insufficiency in patients, which is a lack of adrenal function; however, the rates and severity at which this occurs in patients are still poorly studied. We studied patients with 66 treated adrenal glands using SAbR, which demonstrated that this technique was effective at controlling cancer sites with a control rate of 75% at 1 year. The risk of patients developing adrenal insufficiency in the entire cohort was significant at 14%, with a median time of 4.3 months. There was a higher risk in patients who had both adrenal glands treated with SAbR, or who had received a prior surgical removal of their other adrenal gland prior to SAbR therapy, with 44% of these patients developing adrenal insufficiency. Background: Adrenal metastases are often treated with stereotactic ablative radiation (SAbR). We aimed to assess the incidence, timing, and factors associated with the development of primary adrenal insufficiency (PAI) following SAbR. Methods: A retrospective cohort study comprised 66 consecutive patients (73% men, median age 61 years) who underwent SAbR for adrenal metastasis. Results: The series encompassed metastases from renal cell carcinoma (41%), lung tumors (38%), colorectal adenocarcinoma (9%), melanoma (5%), and others (7%). Median follow-up was 17 months from SAbR. Nine (14%) patients developed PAI at a median of 4.3 months (range, 0.7–20.2). The incidence of PAI was 44% in patients with prior adrenalectomy receiving unilateral SAbR, 44% with bilateral SAbR, 2% with unaffected contralateral gland, and 0% with bilateral metastases treated with unilateral SAbR. PAI was associated with prior adrenalectomy (odds ratio [OR] 32) and bilateral SAbR (OR 8.2), but not age, sex, metastasis size, or biological effective dose. Post-SAbR 6-month and 1-year local control rates were 82% and 75%, respectively. Conclusions: Patients undergoing SAbR for adrenal metastasis are at high risk of developing PAI. PAI is associated with bilateral SAbR and contralateral adrenalectomy. PAI is unlikely with a remaining unaffected adrenal gland or in the setting of bilateral adrenal metastases with unilateral SAbR. [ABSTRACT FROM AUTHOR]