Phase II clinical trial with high-dose methotrexate therapy and citrovorum factor rescue.

One hundred and thirty-four patients with advanced malignant disease were treated with 496 infusions of high-dose methotrexate (HD-MTX) followed by citrovorum factor rescue. Most patients had failed to respond to previous combination chemotherapy. The overall response rate was 29% with 33 partial responses and six complete responses observed in patients with a variety of tumors. Plasma MTX levels were monitored in all patients during each course of therapy in order to identify those patients with delayed plasma MTX clearance. Patients with abnormally slow rates of plasma MTX decay received escalated doses of citrovorum factor rescue in order to prevent drug-induced toxicity. In general, during this study HD-MTX was well-tolerated. Because serious toxicity was neither frequent, severe, nor unpredictable, its use was not limited. HD-MTX should now be evaluated in well-designed controlled clinical trials to compare its antitumor activity to that of conventional- or standard-dose MTX regimens in diseases where HD therapy appears to have efficacy.