Immunotherapy with irradiated tumour cells and BCG in experimental osteosarcoma

The effects of immunotherapy with irradiated tumour cells and BCG were studied in non-metastasizing variety of the Dunn osteosarcoma transplantable in mice. Experimental animals which had been preimmunized with three injections of 0.7 to 1.4 X 10(6) irradiated tumour cells each 1 to 3 weeks before administration of 1 X 10(6) living tumour cells, showed a tumour incidence of 23 per cent. This was significantly (P less than 0.005) lower than the 92 per cent tumour incidence in the control animals. Non-specific immunotherapy with BCG given subcutaneously at a dose of 1.0 mg of dry-weight bacterial mass three times at 3-week intervals was found to have no protective effect against the osteosarcoma. The tumour incidence was 90 per cent for BCG-treated and 94 per cent for control animals. The osteosarcomas were studied light and electron microscopically and also with regard to the histochemical alkaline phosphatase activity. No structural difference was found between the tumours of the various groups. The demonstrated immunotherapeutic response is in contrast to the low degree of immunogenicity of the osteosarcoma, which we will report elsewhere.