Immunotherapy as part of combinations for the treatment of cancer

Immunotherapy (biological therapy) comprises such things as active specific immunotherapy ("cancer vaccines"), nonspecific immunostimulation with cytokines, and the inhibition of suppressor influences exerted or elicited by the tumor. Just as cancer chemotherapy began with the use of single agents and evolved into combination therapy, so immunotherapeutic agents have been combined with each other and with chemotherapy. The alkylating agent cyclophosphamide (Cytoxan; CY) has been used for many years to inhibit tumor-derived suppressor influences in rodents, and has been exploited for the same use in humans. Combinations of CY and cancer vaccines such as autologous tumor cells, Melacine, large multivalent immunogen (LMI), and Theratope have been tested with some success in humans for more than a decade. In this use, the CY is a biological response modifier rather than an antitumor agent. Delayed treatment with CY in treating mouse plasmacytomas has proved more effective than immediate treatment, probably because it allows immunity to develop in the host. CY and moderate-dose interleukin-2 (IL-2) have also been a useful regimen in treating human melanomas. IL-2 is itself a useful component of combination immunotherapy, such as with melanoma peptide vaccines, or with interferon-alfa-2b, (IFN-a), as a dual combination or part of a biochemotherapy regimen. IL-2 and histamine, to block reactive oxygen species, may be a more useful combination for treatment of liver metastases of melanoma than IL-2 alone. In this combination, the histamine may permit continued, unimpeded activity of cytolytic T lymphocytes. Several different combinations of drugs and biological agents have been used as biochemotherapy for melanoma, but although there are higher immediate response rates, the long-range survival benefits have been marginal, not justifying the severe toxicity. Combinations of 5-fluorouracil (5-FU) and IFN-a or levamisole have had efficacy in colon and head and neck cancers, but here the biological agents acted as biochemical modulators. Trials of antibodies and chemotherapy have been limited. It appears that trastuzumab (Herceptin) potentiates antitumor therapy in breast cancer and also increases the cardiotoxicity of those regimens.