Biologic therapy of gastrointestinal cancer.

While there has been some progress in the biologic therapy of colorectal cancer, much work remains to be accomplished. Continued discoveries regarding the immunological response to tumor will ensure the way for future progress. While it is unlikely that cytokine or biologic therapy as we know it will be pursued, cytokines may become an important adjunct in radioimmunoconjugate therapy to improve the number of antibody targeting sites or access of antibody to the targets. In vaccine strategies, cytokines such as GM-CSF may be useful to recruit antigen-presenting cells. Molecular genetic strategies to alter normal or malignant cells to overproduce certain cytokines at selected sites may also augment vaccine efficacy. Finally, an improved understanding of appropriate antigens for vaccination as well as the development of strategies to overcome immune tolerance (without adding toxicity) will be critical to the success of these approaches.