Platelet-derived growth factor receptor inhibitor imatinib mesylate and docetaxel: A modular phase I trial in androgen-independent prostate cancer: Mathew P, Thall PF, Jones D, Perez C, Bucana C, Troncoso P, Kim SJ, Fidler IJ, Logothetis C., Department of Genitourinary Medical Oncology, Unit 427, The University of Texas M.D. Anderson Cancer Center, 1515 Holcombe Blvd, Houston, TX. J Clin Oncol 2004;22:3323–9

Abstract

Purpose To study the platelet-derived growth factor receptor (PDGFR) inhibitor imatinib mesylate in androgen-independent prostate cancer (AIPC), alone and in combination with docetaxel, we designed a modular phase I trial. Our goals were to [1] evaluate the toxicity and maximum-tolerated dose of docetaxel with imatinib, and [2] evaluate the decline of prostate-specific antigen (PSA) induced by imatinib alone, and imatinib and docetaxel. Patients and methods Twenty-eight men with AIPC and bone metastases were enrolled to receive imatinib 600 mg daily lead-in for 30 days, then imatinib 600 mg daily and one of six possible doses of docetaxel weekly for 4 weeks every 6 weeks. Results During the imatinib lead-in module, one dose-limiting toxicity (DLT) event was observed, while two (7%) of 28 had PSA decline (both 2 , in three of four patients at docetaxel 45 mg/m 2 , and in five of six patients at docetaxel 35 mg/m 2 . DLTs (n = 40 total events) were principally fatigue (35%) and nausea (20%). Eight (38%) of 21 had PSA decline greater than 50%, and six (29%) of 21 had PSA decline less than 50%. Serial PSA declines beyond 18 months were observed. PDGFR-expressing tumor declined on serial bone marrow biopsies with combination therapy alone. Conclusion With imatinib 600 mg daily, the maximum-tolerated dose of docetaxel was determined to be 30 mg/m 2 weekly for 4 weeks every 6 weeks. Long-term responses were observed. The role of imatinib in modulating outcomes to docetaxel in AIPC is being tested in a randomized phase II trial.