Combined treatment of syngeneic murine tumors and xenotransplanted human lung cancer by immunotherapy and radiotherapy.

The synergistic effect of nonspecific immunotherapy with cell-wall skeleton of BCG on radiotherapy against two syngeneic murine tumors, a methylcholanthrene-induced tumor (MCA) and a spontaneous well-differentiated mammary adenocarcinoma (Br-1), was studied in (+/+) balb/c mice and (nu/nu) mice of BALB/c background. Single irradiation of tumors with a dose of 2000 rad induced complete shrinkage in about 18% of MCA and Br-1 tumors in (+/+) mice. Single irradiation did not induce complete shrinkage of tumors in (nu/nu) mice. When immunotherapy was combined with radiotherapy, the rates of complete shrinkage of MCA and Br-1 tumors increased to 82 and 61%, respectively. In contrast, such a strong synergistic effect was not observed in (nu/nu) mice. Moreover, human lung cancers (two squamous cell carcinomas and two small cell carcinomas) xenotransplanted to nude mice were treated with the combined therapy. The effect was stronger on squamous cell carcinomas than on small cell carcinomas.