Phase II Study of Imatinib Mesylate in Patients with Prostate Cancer with Evidence of Biochemical Relapse After Definitive Radical Retropubic Prostatectomy or Radiotherapy

Objectives

Patients with biochemical recurrence of prostate cancer after definitive or salvage local therapy in the absence of metastatic disease represent a group well suited to a novel therapeutic intervention. Imatinib mesylate (Gleevec) is a protein-tyrosine kinase inhibitor that has previously been tested in men with androgen-independent and metastatic prostate cancer. This Phase II study was undertaken to determine the safety and efficacy of imatinib mesylate in men with biochemical relapse of nonmetastatic, androgen-sensitive prostate cancer after local therapy.

Methods

Twenty-seven patients were treated with imatinib mesylate 400 mg twice daily for up to 12 months. Three patients (11%) completed less than 4 weeks of therapy and were included in the intent-to-treat analysis of the response to therapy.

Results

Of the 27 patients treated, 5 (18.5%) had a stable prostate-specific antigen (PSA) during the course of treatment; 2 patients (7.4%) experienced a partial response. The remaining 20 patients (74.1%) demonstrated PSA progression. The median progression-free survival was 3 months. The proportion of patients achieving a partial PSA response during therapy did not significantly differ from the null rate of 5% (P = 0.394). Seven patients (25.9%) discontinued therapy secondary to grade 1 to 3 toxicities. No irreversible National Institutes of Health Common Toxicity Criteria grade 3 or 4 toxicities occurred. Grade 3 and 4 toxicity included leukopenia (3.7%), serum glutamic-oxaloacetic transaminase (3.7%) and serum glutamic-pyruvic transaminase (3.7%) elevation, and rash (18.5%).

Conclusions

The results of our study have demonstrated that imatinib mesylate delivered at a dose of 400 mg twice daily is associated with a moderate degree of toxicity and a limited PSA response in this patient population.