Phase II study of sequential chemotherapy with cisplatin (P) in combination with infusional 5FU/LV (PFL) followed by irinotecan (IR) + 5FU/LV (IrFL) followed by docetaxel (T) + 5FU/LV (TFL) in patients (pts) with metastatic gastric carcinoma (MGC) by the Gruppo Oncologico Nord-Ovest (GONO)