Chemical immunosuppression and human cancer

A significant advance in our understanding of cancer is the realization that states of immunodeficiency are associated with an increased incidence of malignancies. Malignant cells have been inadvertently transplanted with homografts obtained from donors with cancer. In the immunosuppressed host such cells have survived, multiplied, and spread. In addition, organ homograft recipients have shown a 5.6% incidence of de novo malignancies at some time after transplantation. Organ transplant recipients who had pre-existing malignancies removed developed recurrences or metastases of the original neoplasms in 41% of cases. Malignancies have also been observed in nontransplant patients treated for a variety of disorders. Cancer chemotherapeutic agents have immunosuppressive side effects; patients have manifested new malignancies while their original tumors were controlled by the antineoplastic drugs. The danger of malignancy makes it imperative that immunosuppressive therapy should only be used when strongly indicated, as in organ transplantation, or where other forms of therapy have failed to control the patient's disease. The use of the appropriate cancer themotherapeutic agents in patients with advanced malignancies is fully justified, as the risk of development of new tumors is far outweighed by the months or years of control of the original neoplasms. Chemotherapy, as an adjuvant to radiotherapy or surgery in the management of localized cancers, should be used with caution as it has yielded disappointing results in many series.