Intervention: Arm B (control): chemotherapy alone, regimen according to each center. Arm A (experimental): surgery (complete tumoral resection; R0) followed by chemotherapy, regimen according to each center. Statistical Analysis: A power analysis showed that to assure a significance level of 0,05 and a beta error 0.20. 168 patients are necessary in each arm. It has been estimated a loss rate of up to 10%.