Impact of monitoring plasma 1,1-dichlorodiphenildichloroethane (o, p′DDD) levels on the treatment of patients with adrenocortical carcinoma

BACKGROUND. It has been suggested recently that 1,1-dichlorodiphenildichloroethane (o, p′DDD) elicits a dose effect relation in the treatment of patients with adrenocortical carcinoma (ACC). The authors performed a single-center, prospective study with two major objectives: 1) to confirm the interest of plasma o, p′DDD level measurement as a prognostic factor of response to o, p′DDD therapy; and 2) to look for parameters associated with a therapeutic plasma o, p′DDD level, especially the daily o, p′DDD dose. METHODS. Since 1995, patients with ACC who were referred to the Gustave-Roussy Institute have been enrolled prospectively in the study. Therapy with o, p′DDD was given as first-line therapy in 13 patients with metastatic disease or as adjuvant therapy in 11 patients. Oral o, p′DDD was given in three separate doses up to at least 6-12 g per day together with substitutive adrenal therapy. Plasma o, p′DDD levels were measured using high-performance liquid chromatography every 2 months. The o, p′DDD therapy was monitored to achieve plasma o, p′DDD levels within 14-20 mg/L. World Health Organization criteria were used to evaluate tumor response and toxicity. RESULTS. Twenty-four patients with ACC were studied, and a plasma o, p′DDD level >14 mg/L was achieved in 14 patients (58%). An objective tumor response was observed in four patients with metastatic lesions (31%): One was response was complete, and three were objective hormonal responses. These tumor responses were observed among the six patients who achieved therapeutic plasma o, p′DDD levels. In contrast, no response was observed among the seven patients with plasma o, p′DDD levels that remained consistently low. Eight of 11 patients who received o, p′DDD as adjuvant therapy had disease recurrence, although the plasma o, p′DDD level was >14 mg/L in 6 patients. Grade 3 or 4 neurologic toxicity was observed in three patients (12%), all with an o, p′DDD level >20 mg/L. The daily o, p′DDD dose was the only parameter associated with the highest plasma o, p′DDD trough levels: It explained 35% of the variability in the plasma o, p′DDD level. A median interval of 3.7 months was found necessary to achieve the highest o, p′DDD trough levels. CONCLUSIONS. The results confirm the prognostic impact of the plasma o, p′DDD level in patients with metastatic ACC and its interest in avoiding toxicity.