Synergistic antitumor effect of interleukin-2 and irradiation on pancreatic cancer in Syrian golden hamsters.

The cooperative effect of interleukin-2 (IL-2) and radiotherapy was studied in pancreatic ductal adenocarcinoma implanted subcutaneously (s.c.) into Syrian golden hamsters. No cooperative antitumor effect was observed in animals given intraperitoneal injections of IL-2 (5 micrograms/hamster) from the 8th day after irradiation. Tumor regrowth was slightly inhibited in animals treated from the 15th and 24th day after irradiation, but the inhibition was not significant. In contrast, when IL-2 was injected intratumorally from the 18th day after irradiation, tumor regrowth was significantly inhibited. It was concluded that the antitumor effect of irradiation was enhanced by IL-2, especially by intratumoral injection after the restoration of immunological competence.