Combination Chemotherapy With or Without Vismodegib in Treating Patients With Advanced Stomach Cancer or Gastroesophageal Junction Cancer

PRIMARY OBJECTIVES: I. To determine if the addition of GDC-0449 (vismodegib) to FOLFOX (fluorouracil, leucovorin calcium, oxaliplatin) chemotherapy improves median progression free survival (PFS) in the first line treatment of patients with advanced gastric and gastroesophageal junction (GEJ) adenocarcinoma. SECONDARY OBJECTIVES: I. To determine if the addition of GDC-0449 to FOLFOX chemotherapy affects overall survival. II. To determine if the addition of GDC-0449 to FOLFOX chemotherapy affects response rate. III. To determine if the addition of GDC-0449 to FOLFOX chemotherapy affects toxicity rates in the first line treatment of patients with advanced gastric and GEJ adenocarcinoma. TERTIARY OBJECTIVES: I. To determine the level of baseline hedgehog pathway activation and correlate with clinical outcome and response to treatment with GDC-0449. II. In those patients who consent to repeat biopsy at week 4-5, hedgehog pathway expression will again be assessed (every attempt will be made to obtain repeat biopsy from the same site as the initial biopsy) and compared to baseline values and clinical outcome. III. To determine a primary gastric cancer gene expression profile that may predict response to GDC-0449. IV. To determine if serum shed collagen epitopes correlate with clinical outcome and may be used to assess efficacy of GDC-0449 treatment. V. To determine if circulating endothelial progenitor cells (EPC)'s correlate with treatment response and may be used to assess efficacy of GDC-0449 treatment. VI. To determine if hedgehog pathway expression is downregulated in EPC's following treatment with GDC-0449. VII. To determine if serum expression of vascular endothelial growth factor (VEGF), transforming growth factor (TGF)-beta, and insulin-like growth factor binding protein (IGFBP) 3 correlate with clinical outcome and may be used to assess efficacy of GDC-0449 treatment. VIII. To determine if human epidermal growth factor receptor 2 (Her2) expression is predictive in assessing the efficacy of GDC-0449 treatment. Of note, Her2 status will be collected retrospectively for those patients who were tested as part of standard of care established in October 2010. OUTLINE: Patients are randomized to 1 of 2 treatment arms. ARM I: Patients receive FOLFOX chemotherapy comprising oxaliplatin intravenously (IV) over 2 hours, leucovorin calcium IV over 2 hours, and fluorouracil IV over 46-48 hours on day 1. Patients also receive placebo orally (PO) once daily (QD) on days 1-14. ARM II: Patients receive FOLFOX chemotherapy as in Arm I. Patients also receive vismodegib PO on days 1-14. In both arms, treatment repeats every 2 weeks in the absence of unacceptable toxicity or disease progression. After completion of study treatment, patients are followed up every 3 months.