Cancer immunotherapy.

Important contributions that stimulated studies in cancer immunotherapy included: (1) the discovery of tumour-associated antigens; (2) the observation that infection with bacille Calmette-Guérin (BCG) in animals was protective against tumour challenge; and (3) the observation that immunodepression due either to malignant disease or to treatment of the disease, was, in some instances, related to prognosis. Immunotherapy trials with microbial agents have involved attempts to obtain a local effect by injecting the agent into the tumour or into the region of the tumour and to obtain a "systemic" effect distant from the site of injection. Trials with active specific immunotherapy involving tumour cells or tumour cell extracts have frequently involved the combination of these specific agents with a nonspecific adjuvant such as BCG. Recent studies with thymosin and levamisole in patients with lung cancer and other types of malignant disease have shown prolonged survival in the groups receiving immunotherapy.