A case report of a TDM-guided optimization of mitotane for a safe and effective long-term treatment

A 43-years old woman was diagnosed an adrenocortical carcinoma (AC) that was excised, whereas two lung metastases were un-operable. Mitotane 6 g/day was started as standard therapy but it was responsible for severe central nervous system (CNS) and gastrointestinal toxicities associated with a 10 kg body weight loss. A therapeutic drug monitoring (TDM) protocol demonstrated that mitotane plasma concentrations (>30 mg/L) exceeded the therapeutic range (14-20 mg/L) and increased even when drug daily dose was reduced by 50%. The increase in drug plasma concentrations was probably due to body slimming. Under continuous TDM control, a reduced mitotane dose (1.5 g/day) was definitively administered and it proved to be tolerable and effective. Indeed, lung metastases were excised and two years later there was no evidence of other neoplastic lesions. In conclusion, the adoption of therapeutic mitotane monitoring allowed the treatment of an AC patient with a reduced, tolerable and effective dose.