A PERSONAL (BIASED) PERSPECTIVE ON CANCER VACCINES

The use of active specific immunotherapy (ASI) for cancer (cancer ''va ccines'') is still in its scientific infancy despite several decades o f clinical and basic research. What has been established is the princi ple that stimulation of the immune response by ''crude'' (i.e., whole cell-derived) vaccines has led, in a proportion of patients, to reject ion of tumor masses, in some instances for 10 years or more. Scientifi c investigations into the nature of recognition of tumor antigenic det erminants (epitopes) by cytolytic T cells have begun to elucidate the mechanisms underlying rejection, making more precise vaccines possible . Yet there should be caution about assuming that a single epitope or even a few epitopes combined will be as effective as the ''crude'' mat erials, which might better be thought of as ''polyvalent.'' ASI in at least one instance may have cured melanoma in a patient with metastati c disease, but that patient developed another immunologically and gene tically distinct melanoma. This may provide an example of both immunol ogical surveillance against the emergence of new melanomas and immunol ogical selection of an immunologically resistant tumor. Combinations o f vaccines with cytokines, cytolytic T cell infusions, or chemotherapy may improve the response rates and durations of survival achievable w ith vaccines alone. The best rationale for synthetically derived vacci nes may be for prophylaxis - that is, as a true vaccine-where the use of tumor-derived materials in normal individuals is difficult to justi fy ethically.