12490 Management Of Autoimmune Hepatitis Under Mitotane Therapy: Reintroduction Of Mitotane Under High Dose Corticosteroids For Targeted Mitotane Therapeutic Levels In A Patient With Recurrent Myxoid Adrenocortical Carcinoma

Abstract Disclosure: T. Hristova: None. D. Fenyves: None. C. Cloutier: None. M. Latour: None. Z. El-haffaf: None. P. Karakiewicz: None. H.J. Olney: None. I. Bourdeau: None. Histologically rare variants of adrenocortical carcinoma (ACC) include myxoid, oncocytic and sarcomatoid subtypes. There are about 50 reported cases of myxoid variants up to now that are described as more aggressive than classical ACC with poorer overall survival. Surgical resection offers the best chance of survival, with mitotane being the first line of treatment after surgery. Mitotane is currently the only approved adrenolytic drug for ACC. Among mitotane adverse effects, auto-immune hepatitis (AIH) is reported in monography, yet barely anything is reported in the literature about it. The precise mechanism of AIH has not been reported yet, but the mainstem therapy of AIH is corticosteroids alone or in combination with azathioprine. We report the case of a 43-year-old male who was diagnosed with non-secreting myxoid ACC subtype stage 2 (7x6x5,5 cm, ki67 18%, Weiss score 6/9). Multigene panel testing revealed a germline pathogenic variant in the ATM gene. Post adrenalectomy, mitotane was initiated within 2 months and increased to 2,5g daily within 6 weeks. 11 weeks after starting mitotane, liver enzymes were as follows: ALT 127 U/L (N: 10-39), AST 54 U/L (N: 13-39), ALP 165 U/L (N: 36-110), GGT 489 U/L (N: 9-47), while pre-mitotane levels were normal. Although mitotane was stopped, ALT increased to 255 U/L and remained high for 10 weeks after its cessation. Liver biopsy showed chronic hepatitis with moderate inflammation which was compatible with toxic hepatitis vs AIH. As kinetic liver enzyme tests increased after mitotane cessation, AIH was the retained diagnosis. Treatment with 40mg prednisone daily was then initiated. Pre-prednisone liver enzymes were ALT 202 U/L, AST 64 U/L, ALP 154 U/L, GGT 216 U/L, whereas 8 weeks later values had decreased to ALT 74 U/L, AST 20 U/L, ALP 108 U/L, GGT 84 U/L, and prednisone was lowered to 15mg daily. ACC recurred 3 months later, about one year after the initial adrenalectomy. After surgical resection, mitotane was restarted at 500mg daily with prednisone 40mg daily. As liver enzymes were within normal ranges, mitotane was slowly increased to 2.5g daily, with mitotane plasma levels of 11.3mg/L, whereas prednisone was decreased gradually to 12.5mg daily. Second ACC recurrence occurred one year later and mitotane was further increased to 3g daily under prednisone 12.5mg reaching mitotane levels up to 21.2 mg/L with surgical debulking. Further therapeutic avenues are being considered for a rapid recent ACC recurrence, such as PARP inhibitors for targeted therapy in the context of ATM gene mutation, but further considerations are required due to previous AIH. To the best of our knowledge this is the first reported case of AIH due to mitotane in a rare ACC subtype in a patient carrying a germline ATM gene mutation. We also report restart of mitotane therapy with concomitant high dose prednisone in the context of ACC recurrence that allowed to reach targeted therapeutic levels. Presentation: 6/1/2024