 The study participants are monitored during adjuvant treatment and following adjuvant treatment. Physical examination, weight and ECOG performance status are assessed at 4- to 26-week intervals. Adverse events are collected using structured forms at the times of the evaluation visits. Blood cell counts and blood biochemistry are measured at 2- to 6-week intervals during imatinib therapy, and at 6-month intervals following completion of adjuvant therapy. CT or MRI examinations of the abdomen and pelvis are performed at 6-month intervals during the study. 