Inclusion Criteria:

- Age 18 or older

- Histologically documented diagnosis of GIST

- Resectable GIST

- GIST removed at open surgery

- Immunohistochemical documentation of GIST (immunostaining for KIT/CD117)

- High risk of tumor recurrence as defined as one of the following: 1) the largest
tumor diameter greater than 10.0 cm (measured by a pathologist, with any mitotic
count); 2) mitotic count over 10 mitoses per 50 high power fields (HPFs) (with any
tumor size); the largest tumor diameter larger than 5.0 cm and the mitotic count is
over 5/50 HPFs; 4) tumor spillage into the abdominal cavity at surgery (or tumor
rupture). No residual tumors must be present at laparotomy, or in postoperative CT or
MRI examinations. Patients who have microscopically infiltrated margins (or suspected
microscopical infiltration, R1) are also allowed to enter study.

- Performance status 0, 1, or 2 (ECOG)

- Adequate organ function, defined as follows: total bilirubin <1.5 x ULN (upper limit
of normal), serum AST (SGOT) and ALT (SGPT) <2.5 x ULN, creatinine <1.5 x ULN, ANC
(neutrophil count) >1.5 x 10^9/L, platelets >100 x 10^9/L.

- Negative pregnancy test (females with childbearing potential)

- Written, voluntary informed consent

Exclusion Criteria:

- Inoperable or metastatic GIST

- Less than 1 week or more than 12 weeks has elapsed from surgery

- Recurrent GIST

- Patient has received any investigational agents within 28 days as calculated from the
first day of the study drug dosing

- Patient is less than 5 years free from another primary malignancy

- Patient with grade III/IV cardiac problems as defined by the New York Heart
Association Criteria

- Female patients who are pregnant or breast-feeding

- Patient has severe or uncontrolled medical disease (i.e. uncontrolled diabetes,
severe chronic renal disease, or active uncontrolled infection). Concurrent use of
warfarin or acetaminophen are not allowed with imatinib.

- Chronic liver disease

- Known diagnosis of human immunodeficiency virus (HIV) infection

- Patient has received chemotherapy for GIST

- Patient has received neoadjuvant imatinib therapy prior to randomization

- Radiotherapy to 25% or more of the bone marrow

- Patient with any significant history of non-compliance to medical regimens or with
inability to grant reliable informed consent