Pre-operative Chemotherapy Plus Bevacizumab With Early Salvage Therapy Based on PET Assessment of Response in Patients With Locally Advanced But Resectable Gastric and GEJ Adenocarcinoma

Inclusion Criteria: * All patients must have microscopically confirmed adenocarcinoma of the stomach or GE junction. Tumors involving the GE junction must have the bulk of their disease in the stomach; tumors of the distal esophagus that extend less than 2cm into the stomach are ineligible for this study. * All patients must be considered candidates for surgical resection. * Patients must have FDG-avid malignancies. * FDG avid tumors are defined as primary tumors with an increased tracer uptake in the region of the tumor that has an SUV \> or = to 3.5 or a tumor:liver ratio \> or = to 1.5, and felt to be "probably" or "definitely malignant" (i.e. likelihood score of 3 or 4) by the reference nuclear medicine physician. * All patients must have localized cancer potentially curable by surgery. The tumor stage should be T any N+ M0 or T3-T4a N any M0(AJCC 7th Edition), by staging that includes a CT scan and either laparoscopy or endoscopic ultrasound. Patients with T1-2 N0M0 or patients with distant metastatic disease (i.e. M1) are ineligible. Any sites of suspected M1 disease by these criteria must be proven to be M0 prior to entrance into the neoadjuvant study. * Patients may not have received prior chemotherapy or radiation for this disease. * The patient is at least 18 years of age. * If female and of child bearing potential, the patient has a negative serum pregnancy test within 14 days of starting therapy, and, if male or female and of child bearing potential, currently uses (and agree to continue to use throughout the study) an acceptable method of birth control (IUD, oral contraceptive, or barrier device). They should agree to continue to use these for three months after the study is completed. The patient also agrees to refrain from nursing during the duration of the study and for at least two months after the study is completed. Pregnant or lactating females are not included because the anti-proliferative effects of bevacizumab may be harmful to the fetus or developing infant. Karnofsky performance status \> or = to 70%. * The patient has adequate hematopoietic function, defined as having a total neutrophil count (ANC) ≥ or = to 1500/mm3, a platelet count ≥ or = 100,000/mm3. The patient has adequate renal and hepatic function, defined as having a serum creatinine ≤ or = to 2.5 mg/dl, urinalysis demonstrating \< 2+ proteinuria and/or a urine protein/creatinine (UPC) ratio \< 1.0. LFTs include a total serum bilirubin ≤ than or = to 2 x ULN, serum AST (SGOT)/ALT (SGPT) and ALK PHOS \< than or = to 2.5 ULN. * The patient has a PT (INR) \< than or = to 1.5 and an PTT \< than or = to 3 seconds above the upper limits of normal (i.e. at MSKCC PTT \< than or = to 37.7 sec) if the patient is not on anticoagulation. * If a patient is on full-dose anticoagulants, the following criteria should be met for enrollment 1. If using warfarin, the subject must have an in-range INR (usually between 2 and 3) and on a stable dose of warfarin. 2. The subject must not have active bleeding or pathological conditions that carry high risk of bleeding (e.g. tumor involving major vessels, known varices). * Ability to understand informed consent and signing of written informed consent document prior to the initiation of treatment. Exclusion Criteria: * Any metastatic disease. * Significant cardiac disease as defined as: * New York Heart Association (NYHA) grade II or greater (see Appendix B for NYHA Class), * congestive heart failure, or history of myocardial infarction or unstable angina within 12 months of study enrollment * Any history of stroke or transient ischemic attack at any time. * Pregnant (positive pregnancy test) or lactating women. A pregnancy test will be performed on sexually active women of childbearing potential prior to entry into the study. Treatment may not begin until the results of the pregnancy test are ascertained. * Inadequately controlled hypertension (defined as systolic blood pressure \> 150 mmHg and/or diastolic blood pressure \> 100 mmHg) on antihypertensive therapy. * Any prior history of hypertensive crisis or hypertensive encephalopathy. * Significant vascular disease (e.g. aortic aneurysm, aortic dissection) * Symptomatic peripheral vascular disease (ie. grade 2 or higher). * Major surgical procedure, open biopsy, or significant traumatic injury within 28 days prior to starting therapy (eg. day 0). * Core biopsy or other minor surgical procedure, excluding placement of a vascular device, within 7 days of starting therapy. * Evidence of bleeding diathesis or coagulopathy. * Proteinuria at screening as demonstrated by either * Urine protein:creatinine (UPC) ratio \> 1.0 at screening, or * Urine dipstick for proteinuria \> or = to 2+ (patients discovered to have \> or = to 2+ proteinuria on dipstick urinalysis at baseline should undergo 24 hour urine collection and must demonstrate \< than or = to 1g of protein in 24 hours to be eligible). * Serious intercurrent infections, or nonmalignant medical illnesses that are uncontrolled or whose control may be jeopardized by the complications of this therapy. * History of abdominal fistula, gastrointestinal perforation, or intra-abdominal abscess within 6 months prior to study enrollment. * Serious, non-healing wound, ulcer, or bone fracture. * Grade 2 or greater pre-existing peripheral neuropathy. * Psychiatric disorders rendering patients incapable of complying with the requirements of the protocol. * Any concurrent active malignancy other than non-melanoma skin cancers, non-metastatic prostate cancer or carcinoma-in-situ of the uterine cervix. Patients with previous malignancies but without evidence of disease for \> 5 years will be allowed to enter the trial. * Clinically significant hearing loss. * EKG evidence of acute ischemia or significant conduction abnormality, as determined by the treating physician. * Known hypersensitivity to Chinese hamster ovary cell products, other recominant human antibodies, or to any component of bevacizumab. * Patients with any other medical condition or reason that, in the investigator's opinion, makes the patient unsuitable to participate in a clinical trial.