A multicenter random assignment phase II study of irinotecan and flavopiridol versus irinotecan alone for patients with p53 wild-type gastric adenocarcinoma (NCI 8060).

Abstract

e14586 Background: Preclinical studies demonstrate that tumors wild-type for p53 (p53wt) are refractory to irinotecan relative to non-functional or mutant p53, and that sequential therapy with flavopiridol, a cyclin dependent kinase inhibitor that inhibits homologous recombination and DNA repair, and irinotecan overcomes p53 mediated drug resistance in vivo. This phase II study is designed to assess cell cycle mediated drug resistance in p53wt gastric cancer, and test the hypothesis that administration of flavopiridol following irinotecan can overcome resistance to irinotecan. Methods: Pts with advanced p53wt (≤ 20% nuclear IHC staining using D07 antibody) gastric adenocarcinoma and disease progression on non-irinotecan chemotherapy regimen were randomized in 2:1 fashion to irinotecan 100 mg/m2 followed 7 h later by flavopiridol 60 mg/m2 administered over 1h or irinotecan 100 mg/m2 administered weekly on a 2 week on/1 week off schedule. Response assessment is performed every 2 cycles and the primary endpoint is 3-month progression free survival (PFS). Pre- and post-treatment biopsies were obtained for molecular assessments of p53 mediated drug resistance. Results: To date 30 of 55 patients screened were p53wt (54%), 19 pts were randomized to receive irinotecan + flavopiridol (n=13) and irinotecan (n=6). Median characteristics of 19 evaluable patients: age 61 (44 to 76), KPS 80% (70 to100), 13 male, 1 prior regimen (1 to 2). The common treatment emergent toxicities were anemia (Grade 2/3 21%), neutropenia (grade 2/3 31%, grade 4 .05%), nausea (grade 2/3 21%) and fatigue (grade 2/3 37%). With irinotecan + flavopiridol 1/13 (8%) confirmed partial response was seen and 5 month disease stabilization in 3/13 (23%) patients. No responses were seen with single agent irinotecan. The median PFS was similar, 1.6 mos irinotecan + flavopiridol vs 1.3 mos in irinotecan group (p=0.21). Conclusions: 54% of gastric cancers are p53wt. Correlative tissue analysis including p53 sequencing, p21, Rad51 is ongoing. Due to lack of activity with irinotecan alone, an amendment to a single arm irinotecan + flavopiridol study is planned.