A prospective analysis of imatinib‐induced c‐kit modulation in ovarian cancer

Abstract

c-Kit and platelet-derived growth factor receptor (PDGFR) are potential molecular targets in epithelial ovarian cancer (EOC). Imatinib inhibits the kinase domain and subsequent downstream signaling of these receptor tyrosine kinases. The objective of this study was to investigate biochemical and biologic effects of imatinib on EOC. Patients with recurrent EOC who had received no more than 4 prior regimens and who had good end-organ function were eligible. Imatinib was administered orally at a dose of 400 mg twice daily in continuous, 28-day cycles with reassessment imaging studies obtained every other cycle. Tumor core biopsies were obtained prior to and at 4 weeks into therapy; microdissected tumor and stroma were subjected to protein lysate array analysis. Blood samples were obtained monthly for cytokine measurements. Twenty-three patients were enrolled, including 16 patients who received imatinib 600 mg daily because of gastrointestinal (GI) toxicity and fluid accumulation at the starting dose. The median time to disease progression was 2 months (range, 2-14 months). Common grade 3 toxicities included edema/ascites/pleural effusions in 11 patients (48%), GI complaints in 8 patients (35%), fatigue in 3 patients (13%), and grade 2 and 3 cytopenias in 10 patients and 3 patients (43% and 13%), respectively. Increased circulating levels of interleukin 6 were associated with grade >/=2 fluid collection (P = .02). A statistically significant trend was observed between pretreatment phosphorylated-kit levels in microdissected tumor and stroma and GI toxicity (P < .01), between tumor levels of epidermal growth factor receptor (EGFR) and PDGFR with grade of fatigue (P </= .005), and EGFR and phosphorylated-AKT levels with grade of ascites and edema (P </= .01). The results of this study indicated imatinib had minimal activity as a single agent in EOC. Its ability to modulate its molecular targets suggests that it may be considered in combinatorial therapy.