Study of Dose Escalation Versus no Dose Escalation of Imatinib in Metastatic Gastrointestinal Stromal Tumors (GIST) Patients

The purpose of this study is to determine if escalating the dose of imatinib to keep the drug blood level at ≥ 1100 ng/ml leads to better outcomes for patients.

• Drug: Imatinib mesylate
  400 mg daily. Number of cycles: until disease progression or unacceptable toxicity develops
  Other Names:

  • Gleevec
  • Glivec
• Drug: Imatinib mesylate
  600 or 800 mg daily. Number of cycles: until disease progression or unacceptable toxicity develops
  Other Names:

  • Gleevec
  • Glivec
• Drug: Imatinib mesylate
  400, 600 or 800 mg daily. Number of cycles: until disease progression or unacceptable toxicity develops
  Other Names:

  • Gleevec
  • Glivec

• Active Comparator: Arm A
  Patients with blood level less than 1100 will continue imatinib 400 mg daily
  Intervention: Drug: Imatinib mesylate
• Active Comparator: Arm B
  Patients with blood level less than 1100 dose adjust imatinib mesylate to goal blood level ≥1100 ng/mL
  Intervention: Drug: Imatinib mesylate
• Active Comparator: Arm C
  Patients with blood level ≥1100 will continue imatinib 400 mg daily
  Intervention: Drug: Imatinib mesylate
• Active Comparator: Arm D
  Patients with tumors that harbor exon 9 mutations will continue imatinib mesylate at 400 mg or dose escalate up to 800 mg daily
  Intervention: Drug: Imatinib mesylate

Inclusion Criteria:

• Age ≥ 18 years
• Unresectable and/or metastatic GIST
• Currently receiving imatinib 400 mg per day for a minimum of 4 weeks prior to registration, and for no more than 6 months prior to registration. This must be the first time that the patient has been treated for metastatic and/or unresectable GIST
• For patients who received imatinib following surgery at the time of an initial diagnosis of GIST, there must be a 6 month interval between completion of imatinib and the diagnosis of metastatic GIST
• Good physical functioning (ECOG Performance Status of 0 or 1)
• Generally, good function of organ such as liver and kidneys

Exclusion Criteria:

• Disease progression during adjuvant therapy with imatinib (adjuvant treatment is treatment that is given after surgery for GIST)
• Known intolerance of imatinib at a dose of 400 mg/day or higher
• Prior systemic therapy for advanced GIST with imatinib or those who have been on imatinib for longer than 6 months for unresectable and/or metastatic disease
• Major surgery within 2 weeks prior to Day 1 of study or who have not yet recovered from prior surgery
• Use of coumadin derivatives (i.e. warfarin, acenocoumarol, phenprocoumon)
• Patients who have received wide field radiotherapy ≤ 4 weeks or limited field radiation for palliation < 2 weeks or who have not recovered from side effects of this therapy