The results of various in vitro analyses indicate there is an active immune 
response against antigens associated with human malignancies. This immune 
response apparently can be augmented by nonspecific immunologic stimulates such 
as BCG. These agents are effective for destroying tumor when injected locally 
into intracutaneous disease but are not as effective for subcutaneous disease. 
Preliminary clinical trials indicated that immune stimulants are effective when 
administered systemically. The effect is only minimal for diseminated disease, 
but the therapeutic benefit is clearly augmented for patients with a minimal 
residual tumor burden, such as those patients with metastases to regional lymph 
nodes. Thus immunotherapy is a systemically active mode of therapy. Its toxicity 
is minimal, and it appears to be effective in a wide spectrum of the disease. 
However, immunotherapy is not effective for a large residual tumor burden; 
consequently it must be used in combination with other modes of treatment such 
as irradiation therapy or chemotherapy. Early experiences with BCG immunotherapy 
for malignant melanoma and C. parvum for oat cell carcinoma are encouraging. It 
is remarkable that a nonspecific immunologic stimulant does, in fact, have this 
effect. Immunotherapy experiments in animals suggest that in order to achieve 
maximal benefit. BCG must have close contact with tumor cells or must be 
combined with a tumor-associated antigen. If these principles are true for man, 
it would seem that improvements for nonspecific immunotherapy in human neoplasms 
would be further augmented if a tumor-related antigen could be extracted from 
human tumours and combined with a nonspecific immunologic stimulant.