Phase I trial of docetaxel administered by weekly infusion in patients with advanced refractory cancer

Docetaxel is a highly active antineoplastic agent; however, grade IV leukopenia occurs in the large majority of patients treated with a dose of 100 mg/m2 every 3 weeks. Recent experience with weekly paclitaxel has demonstrated a bone marrow-sparing effect when a weekly administration schedule is used. We investigated a weekly schedule of docetaxel in an attempt to alter the toxicity profile and improve the therapeutic index.

Thirty-eight patients with advanced, refractory malignancy entered this phase I trial between October 1996 and June 1997. Docetaxel was administered weekly for 6 consecutive weeks, followed by 2 weeks without treatment. Sequential cohorts of patients were treated at the following dose levels: 20, 25, 30, 36, 43, and 52 mg/m2. Patients were reevaluated after one course (8 weeks); patients with objective response or stable disease continued treatment for a maximum of four courses or until disease progression.

Thirty-five patients completed at least one course of therapy. Myelosuppression was not a dose-limiting toxicity (DLT) at any of the doses tested. Only five episodes of grade III leukopenia occurred (14% of patients, 2% of doses), and no grade IV leukopenia was produced. No grade III or IV thrombocytopenia or anemia was observed. Grade III fatigue and asthenia were observed in all three patients treated at 52 mg/m2/wk and in two of 10 at 43 mg/m2/wk. Other grade III toxicity included acral erythema (n = 1), neuropathy (n = 1), peripheral edema (n = 1), and diarrhea (n = 1). The DLTs of this docetaxel schedule are fatigue and asthenia. Although the maximum-tolerated dose by definition of this study was 43 mg/m2/wk, we selected 36 mg/m2/wk for ongoing phase II studies.

The toxicity profile of docetaxel is markedly altered when the drug is administered by a weekly schedule. Myelosuppression is mild and uncommon. Fatigue and asthenia are the DLTs; other nonhematologic toxicities, which included peripheral edema and neuropathy, are uncommon, and the arthralgia/myalgia syndrome was not observed. Weekly administration of docetaxel may provide a better tolerated, efficacious use of this drug; further investigation of weekly docetaxel as a single agent and in combination regimens is warranted.