PSUN24 Adrenal Metastases Treated with Radiotherapy: Development of Adrenal Insufficiency

INTRODUCTION: Adrenal metastases are the second most common neoplasms of the adrenal cortex. Adrenal insufficiency (AI) develops when more than 90% of the cortex is destroyed. In patients with adrenal metastases requiring local treatment, stereotactic ablative radiation therapy (SAbR) has been shown to be well tolerated. Yet, data on the development of AI following adrenal SAbR are scarce. Therefore, we aimed to assess the incidence, timing, and factors associated with the development of AI in patients undergoing SAbR for the treatment of adrenal metastases. Utilizing an IRB approved registry protocol, we conducted a retrospective longitudinal follow-up study to characterize 66 patients (73% men; median age 61 years) with adrenal metastases who underwent SabR, followed for median 3.8 years from the initial cancer diagnosis and 11.5 months from SAbR. The diagnosis of primary AI was based on low morning serum cortisol levels (<5 μg/dL) with >2-fold elevated plasma ACTH, or peak cortisol <18 μg/dL post cosyntropin. Primary carcinomas included renal cell (41%), lung (38%), colorectal (9%), melanoma (5%), and others (7%). Twenty-four (38%) patients had bilateral adrenal metastases. At the time of SAbR, 41 (62.1%) patients had uninvolved contralateral adrenal glands, 16 (24.2%) had bilateral adrenal metastases, and 9 (13.6%) had contralateral adrenalectomy prior to SAbR. Nine patients had bilateral SAbR and 9 had SAbR to one adrenal gland in the setting of contralateral adrenalectomy. Most patients (66.7%) underwent 5 SAbR fractions, with a median dose of 800 cGy/fraction. In our cohort, 39/66 (59%) patients underwent comprehensive assessment of adrenal function. Overall, 7 (10.6%) patients developed post-SAbR AI at median time of 4.3 months (range, 0.7-20.2). The incidence of post-SAbR AI was 22.2% (2/9) in patients with prior contralateral adrenalectomy, 18.8% (3/16) with bilateral adrenal metastases, and 0% (0/41) with normal contralateral adrenal gland. A 6-month-AI-free survival rate was 72.7% (95% CI, 37.0-90.3) in patients with bilateral metastases and 64.8% (1.6-73.7) in patients with contralateral adrenalectomy. Post-SAbR median progression-free survival (local disease) was 3.0 years, with 6-month and 1-year survival rates of 82.4% and 75.0%, respectively. CONCLUSIONS: Our study shows thatpatients with a normal contralateral adrenal gland are unlikely to develop post-SAbR AI. In contrast, AI occurred in ∼ 20% of patients with prior contralateral adrenalectomy or bilateral adrenal metastases. In this high-risk cohort, only 60% of patients underwent assessment of adrenal function. It is crucial to monitor adrenal function in patients undergoing SAbR for adrenal metastasis, especially in those with affected or surgically absent contralateral gland. This study reinforces the importance of a team-based approach to the management of patients with adrenal metastasis to improve patient outcomes. Presentation: Sunday, June 12, 2022 12:30 p.m. - 2:30 p.m.