The principal objectives are to demonstrate the efficacy of treatment, safety, survival and to find out if geriatric assessment data can help to better predict chemotherapy toxicity. The researchers plan to accrue 43 patients diagnosed with locally advanced or metastatic gastric cancer. They will receive FOLFIRI and 4 geriatric evaluations: before treatment, day 1 cycle 2, day 1 cycle 4 and at the end of chemotherapy. These evaluations include tests of cognitive functions (MMS), nutritional status (MNA), co-morbidity (CIRS-G), mobility (Get up and Go), activities (ADL; IADL), quality of life (QLQ-C30), depression (GDS-15) and Lachs-Balducci screening.