[Schedule dependency of i.v.-paclitaxel against SC-M 109 mouse lung cancer]

Although paclitaxel was shown to have a broad spectrum of antitumor activity against various experimental tumors, the optimal treatment schedule of this drug is not yet determined. In the present study, a trial was carried out to determine the optimal treatment schedule of paclitaxel given i.v. against M 109 mouse lung cancer implanted SC. Schedules examined were: day 1 (d 1) single administration, d 1, 5, 9 intermittent administration, and d 1-5 and d 1-9 daily consecutive administration. As the result, a significant increase of the lifespan was firstly demonstrated by d 1-9 schedule. The optimal dose was as low as 6.5 mg/kg/day (20 mg/m2/day, total 180 mg/m2) and no toxicity was observed with respect to the weight loss. Since the concentration and total amount of Cremophor EL (polyoxyethylene castor oil), which is suspected to be a causative agent for high incidence rate of hypersensitivity reactions by clinical formulation of paclitaxel, inevitably decrease in such a low dose setting, these results should be taken into considerations when exploring the optimal schedule of paclitaxel clinically.