Inclusion Criteria:

- The patient must have pathologically confirmed carcinoma of the stomach or GEJ
(Siewert's type I, II, or III); confirmation will be performed locally at each
participating institution

- The patient must have advanced disease not amenable to surgical resection

- Patients must have disease that can be evaluated radiographically; this may be
measurable disease or non-measurable disease; measurable disease is defined as that
which can be measured in at least one dimension as > 20 mm with conventional
techniques, or > 10 mm by high resolution imaging; disease that is identified on
radiology studies, but does not meet the criteria for measurable disease, is
considered non-measurable

- The patient must have received one prior chemotherapy regimen for his or her
unresectable or metastatic disease; this does not include therapy administered in the
adjuvant or neoadjuvant setting

- At least 2 weeks must have elapsed since the patient received prior chemotherapy,
anti-angiogenic therapy, or other targeted therapy; 2 weeks since prior radiation
therapy; or, 4 weeks if the last regimen included carmustine (BCNU) or mitomycin C

- The patient must have a Karnofsky performance status of >= 60

- Serum creatinine =< 2 mg/dl

- Total serum bilirubin =< 2 mg/dl

- If the patient has Gilbert's disease and has a serum bilirubin greater than 2.0
mg/dl, the case must be discussed with the principal investigator; such a
patient may be considered eligible on a case-by-case basis

- Serum aspartate aminotransferase (AST) (serum glutamic oxaloacetic transaminase
[SGOT])/ alanine aminotransferase (ALT) (serum glutamate pyruvate transaminase
[SGPT]) =< 3 times the upper limit of normal, or

- Serum AST (SGOT)/ ALT (SGPT) =< 5 times the upper limit of normal in case of liver
metastases

- White blood cell (WBC) >= 3000/mm^3

- Absolute neutrophil count (ANC) >= 1000/mm^3

- Platelets >= 75,000/mm^3

- The patient must have available tumor tissue for assessment of p53 status by
immunohistochemistry (IHC) (=< 20% cutoff for positivity)

- Tumor must be p53 wild type as defined as =< %20 nuclear staining on
immunohistochemistry

- Women of child-bearing potential and sexually active males must be counseled to use
an accepted and effective method of contraception (including intrauterine device
[IUD], oral contraceptives, or barrier devices) while on treatment and for at least
two months after their last treatment on this study; woman also must agree to refrain
from nursing during the duration of this study and for at least two months after
their last treatment on this study; women of child-bearing potential must have a
negative serum pregnancy test to be eligible for this study

- The patient must have the mental capacity to understand the nature of this study and
provide informed consent to participate

Exclusion Criteria:

- The patient may not have previously received irinotecan or flavopiridol

- The patient may not be receiving any other investigational agents

- The patient may not have any ongoing grade 2 or greater toxicity from a prior
treatment

- The patient may not have an ongoing uncontrolled illness including, but not limited
to active infection, symptomatic congestive heart failure, myocardial infarction in
the past 6 months, or new cardiac arrhythmia in the past 6 months

- Patients with a diagnosis of active human immunodeficiency virus (HIV) infection, on
anti-retroviral therapy, or with a cluster of differentiation 4 (CD4) count less than
200 are ineligible due to potential interactions between irinotecan, flavopiridol,
and anti-retroviral medications as well as possible immunosuppressive activity of the
study treatment