Imatinib Mesylate With or Without Bevacizumab in Treating Patients With Metastatic or Unresectable Gastrointestinal Stromal Tumor

PRIMARY OBJECTIVES:

I. To determine whether treatment with imatinib (imatinib mesylate) plus bevacizumab leads
to improved progression free survival (PFS) versus treatment with imatinib alone in
first-line treatment of incurable gastrointestinal stromal tumor (GIST).

SECONDARY OBJECTIVES:

I. To compare response probabilities (confirmed and unconfirmed complete response [CR] and
partial response [PR] for subset of patients with measurable disease), overall survival, and
central-review based progression-free survival (CRb-PFS) in patients treated with imatinib
and bevacizumab versus those treated with imatinib alone.

II. To compare the frequency and severity of toxicities associated with imatinib plus
bevacizumab versus imatinib alone.

TERTIARY OBJECTIVES:

I. To explore the association between soluble vascular endothelial growth factor (VEGF),
VEGF-factor D (VEGF-D), VEGF receptor (VEGFR)-1, VEGFR-2, angiopoietin-2 (Ang-2),
platelet-derived growth factor receptor (PDGFR)-AA and PDGFR-BB levels, positron emission
tomography (PET) imaging and immunohistochemistry for cyclin-dependent kinase inhibitor 2A
(p16), VEGF and VEGFR, with kinase mutation status and clinical outcomes.

II. To explore imatinib pharmacokinetics with single nucleotide polymorphisms involving the
adenosine triphospate (ATP)-binding cassette, sub-family G (WHITE), member 2 (ABCG2) and
cytochrome P450, family 3, subfamily A, polypeptide 4 (CYP3A4) genes, as well as other genes
that are reported to influence the absorption, distribution, metabolism and elimination of
imatinib.

OUTLINE: Patients are randomized to 1 of 2 treatment arms.

ARM I (CLOSED TO ACCRUAL 10/1/2009): Patients receive imatinib mesylate orally (PO) once
daily (QD) on days 1-21 and bevacizumab intravenously (IV) over 30-90 minutes on day 1.

ARM II (CLOSED TO ACCRUAL 10/1/2009): Patients receive imatinib mesylate PO QD on days 1-21.

In both arms, courses repeat every 21 days in the absence of disease progression or
unacceptable toxicity.

After completion of study treatment, patients are followed at 1 month, every 6 months for 2
years, and then annually for 5 years.

Inclusion Criteria:

- REGISTRATION # 1

- Patient must have a biopsy proven diagnosis of gastrointestinal stromal tumor (GIST)
that is distantly metastatic or unresectable; patients must be determined to be
unresectable for cure

- Patient may have measurable and/or non-measurable disease; computed tomography (CT)
or magnetic resonance imaging (MRI) used for measurable disease must have been
completed within 28 days prior to registration; CT or MRI used for non-measurable
disease must have been completed within 42 days prior to registration; PET scans are
not sufficient for disease assessment; all disease must be assessed and documented on
the Baseline Tumor Assessment Form

- CT/MRI scans must be performed and submitted for central review; archived tissue must
be submitted as outlined

- Institutions must seek additional patient consent for PET scans as outlined; if
patient consents to the submission of PET scans, the patient must also be registered
to Registration #2

- Patient must not have known brain metastasis

- Patient must have a Zubrod performance status of 0 - 3

- Patient must have resolution of transient toxicities from any prior chemotherapy,
radiation therapy or surgery to =< grade 1 (Common Terminology Criteria for Adverse
Events [CTCAE] version 3.0)

- Patient may have previously received traditional chemotherapeutic agents in any
setting, provided at least 28 days have elapsed since completing chemotherapy and
they have recovered to =< grade 1 from all drug-induced toxicities

- Patient must not have received prior treatment with bevacizumab or other agents
targeting VEGF, VEGFR, or PDGFR for advanced disease; those agents may have been used
in the adjuvant setting if the patient did not recur for at least 12 months following
the completion of treatment; patients may be receiving imatinib for advanced disease
prior to registration provided they meet ALL of the following criteria:

- Patient must not have received more than 30 days of imatinib treatment prior to
registration

- Patients have not been restaged; (baseline disease assessments prior to
initiation of imatinib must fulfill requirements)

- Patients must have no clinical signs of progression

- Prior radiotherapy is allowed, provided at least 28 days have elapsed since the last
treatment and there is evidence of progressive disease within the radiation field or
disease outside the radiation field

- Patient must not have had a major surgical procedure, open biopsy, or significant
traumatic injury within 28 days prior to registration, or anticipation of need for
major surgical procedure during the course of the study; no fine needle aspirations
or core biopsies are allowed within 7 days prior to registration; no procedure to
place a port-a-cath is allowed within 7 days prior to registration

- Patient must have a total bilirubin =< 2.0 x institutional upper limit of normal
(IULN), obtained within 28 days prior to registration

- Patients without liver involvement must have serum glutamic oxaloacetic transaminase
(SGOT) or serum glutamate pyruvate transaminase (SGPT) =< 2.5 x IULN, obtained within
28 days prior to registration; patients with liver involvement must have SGOT or SGPT
=< 5 x IULN

- Patient must have adequate renal function as defined by a serum creatinine =< 1.5 x
IULN obtained within 28 days prior to registration

- Patient must have urine protein/creatinine ratio (UPC) < 1; this result must be
obtained within 28 days prior to registration

- Patient must have an absolute neutrophil count (ANC) >= 1,000/mcl obtained within 28
days prior to registration

- Patient must have a platelet count >= 100,000/mcl obtained within 28 days prior to
registration

- Patient must have hemoglobin >= 9 gm/dl (this may be achieved by transfusion if
needed) obtained within 28 days prior to registration

- Patient must have an international normalized ratio (INR) =< 1.5, obtained within 28
days prior to registration

- Patient must have a partial thromboplastin time (PTT) =< IULN, obtained within 28
days prior to registration

- Patient must not be taking therapeutic doses of Coumadin (warfarin) as
anticoagulation at the time of registration; patients requiring therapeutic
anticoagulation may use low-molecular weight heparin (e.g., Lovenox) or other agents,
and mini-dose Coumadin (1 mg PO QD) as prophylaxis is allowed

- Patient must not have had a cerebrovascular accident (CVA), transient ischemic attack
(TIA), myocardial infarction or unstable angina within 6 months prior to
registration; patient must not have serious cardiac arrhythmia requiring medication,
New York Heart Association (NYHA) class II or greater congestive heart failure, or
clinically significant peripheral vascular disease

- Patient must not have had an abdominal fistula, gastrointestinal perforation or
intraabdominal abscess within 28 days prior to registration

- Patient must not plan to use other investigational agents while on protocol treatment

- Patient must have no contraindication to oral medications (e.g., severe dysphagia);
patients with gastrostomy (G)- or jejunostomy (J)- tubes are eligible

- Patient must not have blood pressure > 160/90; patients with a history of
hypertension must be on a stable regimen of anti-hypertensive therapy

- Patient must not have a serious, non-healing wound, ulcer, or bone fracture

- Patient must not be pregnant or nursing; male and female patients of reproductive
potential must agree to employ an effective barrier method of birth control
throughout protocol treatment and for up to 6 months following discontinuation of
study drugs

- No other prior malignancy is allowed except for the following: adequately treated
basal cell or squamous cell skin cancer, in situ cervical cancer, adequately treated
stage I or II cancer from which the patient is currently in complete remission, or
any other cancer from which the patient has been disease free for five years

- If day 28 or 42 falls on a weekend or holiday, the limit may be extended to the next
working day; in calculating days of tests and measurements, the day a test or
measurement is done is considered day 0; therefore, if a test is done on a Monday,
the Monday four weeks later would be considered day 28

- All patients must be informed of the investigational nature of this study and must
sign and give written informed consent in accordance with institutional and federal
guidelines

- At the time of patient registration, the treating institution's name and
identification (ID) number must be provided to the Data Operations Center in Seattle
in order to ensure that the current (within 365 days) date of institutional review
board approval for this study has been entered into the data base

- REGISTRATION #2 - PET SUBSTUDY:

- Patient must have been registered to the main study

- Patient must have consented to the submission of PET scans