High-dose mitotane strategy in adrenocortical carcinoma: prospective analysis of plasma mitotane measurement during the first 3 months of follow-up

Background: The benefit-to-risk ratio of a high-dose strategy at the initiation of mitotane treatment of adrenocortical carcinoma (ACC) remains unknown. Methods: To evaluate the performance of a high-dose strategy, defined as the highest tolerated dose administered within 2 weeks and maintenance therapy over 4 weeks, we conducted a single-center, prospective study with two main objectives: to evaluate the percentage of patients who achieve a plasma mitotane level above 14 mg/l and to evaluate the tolerance of mitotane within the first 3 months of treatment. Plasma mitotane levels were measured monthly using HPLC. Results: Twenty-two patients with ACC were prospectively enrolled. The high-dose mitotane strategy (4 g/day or more in all patients, with a median of 6 g/day within 2 weeks) enabled to reach the therapeutic threshold of O14 mg/l at 1, 2, or 3 months in 6/22 patients (27%), 7/22 patients (32%), and 7/22 patients (32%) respectively. In total, a therapeutic plasma mitotane level was reached in 14 out of 22 patients (63.6%) during the first 3 months in ten patients, and after 3 months in four patients. Grade 3-4 neurological or hematological toxicities were observed in three patients (13.6%). Conclusion: Employing a high-dose strategy at the time of mitotane initiation enabled therapeutic plasma levels of mitotane to be reached within 1 month in 27% of the total group of patients. If this strategy is adopted, we suggest that mitotane dose is readjusted according to plasma mitotane levels at 1 or/and 2 months and patient tolerance.