Effects of combined radiotherapy and immunotherapy with the use of pyran copolymer on murine fibrosarcoma.

A weakly immunogenic, 3-methylcholanthrene-induced, subcutaneous fibrosarcoma syngeneic to inbred C3H/HeJ mice was used. Pyran copolymer was injected either directly into the tumor, ip, or iv as soon as tumors appeared or when tumors were 8 mm in diameter. One, three, or five doses of pyran copolymer at 10 or 20 mg/kg/dose were injected, with multiple doses being given every other day. Pyran copolymer injected intratumorally once, three times, or five times significantly retarded tumor growth and prolonged the survival times of the hosts. Of the other routes and doses, only pyran copolymer given three times iv significantly retarded tumor growth, but none of these significantly prolonged the survival times of the hosts. Pyran copolymer alone did not induce any complete regression of tumor. Local tumor irradiation with a single exposure to 2,000 rads of X-ray induced complete regressions in some mice, but a higher percentage of tumor cure was observed when tumor irradiation was followed by pyran copolymer treatment.