While new treatments for metastatic and recurrent colorectal cancer have become available over the past several years, this disease remains incurable with a limited life expectancy from the time of diagnosis. New strategies for treatment of disseminated colorectal cancer are needed. Under this proposal, patients with advanced colorectal cancer will receive Granulocyte-Macrophage Colony-Stimulating Factor (GM-CSF) to stimulate endogenous dendritic cells and enhance anti-tumor immune mechanisms. This will be combined with standard chemotherapy and patients will be followed for response and overall survival. Detailed correlative laboratory analysis will also be performed to define the extent of dendritic cell and cellular immune system stimulation.

Inclusion Criteria:

• Patient must have: metastatic, disseminated or recurrent colon or rectal cancer
• Patient to receive weekly or biweekly chemotherapy for at least 4 cycles (4 weeks) Examples include: 5FU or 5FU/leucovorin given once weekly Irinotecan (single agent) given once weekly 5FU/leucovorin/irinotecan given once weekly
• Patient must be able to be taught to administer GM-CSF subcutaneously

Exclusion criteria:

• Known allergic or other adverse reaction to GM-CSF
• Chemotherapy administration more frequently than bi-weekly
• Pregnant or lactating women