Spironolactone is associated with reduced mitotane levels in adrenocortical carcinoma patients

Adrenocortical carcinoma (ACC) is a rare endocrine malignancy with a poor prognosis. Mitotane, a derivative of the pesticide DDT, has been used successfully as first line chemotherapy since the 1960s, if maintained within a narrow therapeutic window. Spironolactone (SPL) is frequently used to treat glucocorticoid excess-associated adverse effects such as severe hypokalemia. Although data of a previous case report indicate a link, valid data regarding SPL use and mitotane plasma concentrations in a human cohort are lacking. This retrospective analysis includes data from 54 mitotane-receiving ACC patients (14 co-administered with SPL) treated between January 2005 and April 2020 (20 male, mean age 54.1 ± 2.2 yrs). All available mitotane concentrations, treatment doses, tumor stage and evidence of hormone activity were collected. Primary outcomes included mitotane levels and concentration/dose-ratios as well as time-in-range in patients with and without additional SPL treatment. The SPL group was characterized by higher glucocorticoid secretion. Other features such as tumor stage, size and anthropometrics were similar between groups. Interestingly, the SPL group had significantly lower mitotane levels despite higher doses. Mitotane time-in-range was significantly reduced in the SPL group, as was time-in-range to progression. These data provide first evidence in a human cohort for potential SPL-mitotane interactions (beyond mentioned case report), which affect dose response and may modulate treatment outcomes. This should caution clinicians to carefully adjust mitotane doses during SPL treatment in ACC patients or choose alternative therapeutic options.