8691 Recovery Of Adrenal Function After Stopping Mitotane In Patients With Adrenocortical Carcinoma

Abstract

Abstract Disclosure: B. Altieri: None. O. Kimpel: None. F. Megerle: None. M. Detomas: None. I.O. Chifu: None. C.T. Fuss: None. M. Quinkler: None. M. Kroiss: None. M. Fassnacht: None. Background: Mitotane is the standard therapy of adrenocortical carcinoma (ACC), both adjuvantly in patients with high risk of recurrence and palliative setting, due to its relative selectivity of its cytotoxic effects towards adrenocortical cells. Therefore, it virtually always leads to adrenal insufficiency. However, frequency and characteristics of hypothalamic-pituitary-adrenal (HPA) axis recovery after discontinuation are not well defined. Methods: Retrospective study of patients with ACC adjuvantly treated with mitotane for ≥12 months who were disease-free at mitotane stop and had a minimum follow-up ≥1 year. Data on patients and tumor characteristics, mitotane treatment, and information on HPA axis were analyzed. Primary endpoint was the adrenal recovery. Explorative analysis of predictive factors (e.g. sex, age, follow-up in reference center, cumulative mitotane dose and plasma levels, duration of treatment, and dose of hydrocortisone-equivalent replacement) was performed using Cox regression. Mitotane plasma elimination rate and hormonal changes after mitotane stop were also investigated. Results: 56 patients (36 women) treated with mitotane for a median time of 25 months and an average daily dose of 2.8 g (interquartile range 1.8-3.4) were included. The average hydrocortisone-equivalent replacement daily dose during mitotane treatment was in median 49.4 mg (41.1-53.5). Mitotane plasma levels decreased slowly after discontinuation, but with a very high variability between individual patients. Median time until mitotane levels dropped below 5 mg/L, 2 mg/L, and the detection limit was 152 days (114-202), 280 days (192- 37 370), and 395 days (227-546), respectively. Full adrenal recovery was documented in 32 (57%) patients after a median time of 26 months (95%CI=19.6-32.4). Among these, 22 (69%) achieved HPA recovery within 24 months. To note, a complete recovery after more than 67 months did not occur. Partial and insufficient recovery were observed in 10 (18 %) and 14 (25%) patients, respectively. In four patients (7.1%) adrenal insufficiency persisted >5 years after discontinuation. Mitotane peak ≥27mg/L significantly correlated with longer time to adrenal recovery (HR=0.2, 95%CI=0.1-0.8, p=0.03). 27/38 patients (71%) followed in reference centers achieved adrenal recovery compared to only 5/18 (28%) followed-up in non-reference centers (HR=4.51, 95%CI=1.71-11.89, p=0.002). Other investigated factors were not associated with adrenal function after discontinuation. Conclusions: Our study demonstrates that adrenal recovery occurs in most patients after stopping mitotane, particularly when followed-up in specialized centers, but not in all. Elimination time of mitotane after treatment discontinuation is very long, but individually quite variable. Presentation: 6/2/2024