A Phase I trial of protracted oral fixed-dose temozolomide

The current Phase I trial was conducted to determine the dose-limiting toxicity (DLT), maximum tolerated dose, and recommended Phase II dose of oral fixed-dose temozolomide when administered for 5 of every 7 days on a continuous basis.

Patients received a fixed dose of temozolomide daily for 5 of every 7 days continuously. Four weeks of treatment were considered 1 treatment cycle. Patients were accrued at 7 different dose levels ranging from 100 mg/day to 360 mg/day.

Forty-six patients received 111 cycles of therapy. DLT consisted of myelosuppression, particularly thrombocytopenia. The primary nonhematologic toxicities were nausea and emesis, which were easily controlled with antiemetics.

Protracted administration of temozolomide at a fixed dose of 300 mg/day for 5 of every 7 days continuously was well tolerated and allowed greater dose intensity compared with various other schedules. This regimen could potentially increase antitumor activity as protracted temozolomide schedules inhibit DNA repair by depletion of the repair protein O6-methylguanine-DNA methyltransferase.