A personal (biased) perspective on cancer "vaccines"

The use of active specific immunotherapy (ASI) for cancer (cancer "vaccines") is still in its scientific infancy despite several decades of clinical and basic research. What has been established is the principle that stimulation of the immune response by "crude" (i.e., whole cell-derived) vaccines has led, in a proportion of patients, to rejection of tumor masses, in some instances for 10 years or more. Scientific investigations into the nature of recognition of tumor antigenic determinants (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" materials, which might better be thought of as "polyvalent." ASI in at least one instance may have cured melanoma in a patient with metastatic disease, but that patient developed another immunologically and genetically distinct melanoma. This may provide an example of both immunological surveillance against the emergence of new melanomas and immunological selection of an immunologically resistant tumor. Combinations of vaccines with cytokines, cytolytic T cell infusions, or chemotherapy may improve the response rates and durations of survival achievable with vaccines alone. The best rationale for synthetically derived vaccines may be for prophylaxis-that is, as a true vaccine-where the use of tumor-derived materials in normal individuals is difficult to justify ethically.