Purpose: To investigate sequence effects on toxicity, tumor response and pharmacokinetics of docetaxel and carboplatin, together with a determination of the maximum-tolerated dose (MTD) and recommended dose for each schedule.
Patients and methods: A total of 46 chemotherapy-naive patients with advanced non-small-cell lung cancer were randomized to receive docetaxel before (schedule A) or after (schedule B) carboplatin. The dose levels studied were [docetaxel (mg/m(2))/carboplatin (mg x min/ml)] 50/5, 60/5, 60/6, 60/7, and 70/6. Treatment cycles were repeated every 3 or 4 weeks unless disease progression or undue toxicity occurred.
Results: Of the 46 patients, 44 were assessable for toxicity and received a total of 84 cycles. The major dose-limiting toxicity was neutropenia. When the docetaxel dose was 60 mg/m(2), the carboplatin MTD was deemed to be AUC 7 in both schedules. When the docetaxel dose was escalated to 70 mg/m(2), the carboplatin MTD was reached in schedule A, and the dose-limiting toxicity was not observed in schedule B. Tumor response was observed in 4 of 22 patients (18%) with schedule A and 8 of 19 (42%) with schedule B. Clearances of both drugs were not affected by sequence: 111.2+/-26.8 ml/min and 107.8+/-29.0 ml/min for carboplatin (P=0.69), and 26.7+/-8.3 l/h and 22.8+/-7.0 l/h for docetaxel (P=0.19) in schedules A and B, respectively.
Conclusions: Carboplatin AUC 6 followed by docetaxel 70 mg/m(2) was a favorable regimen for phase II study because of likely lower toxicity and a potentially higher response rate than the reverse sequence schedule. The mechanism of the sequence effects on toxicity and tumor response could not be explained by the pharmacokinetic interactions.