Radiation Responses of Subrenally Transplanted Syngeneic and Allogeneic Mouse Fibrosarcomas

The radiation responses of two tumor types transplantable into C3H/He mice and differing in radiosensitivity, i.e., 3‐methylcholanthrene (MCA)‐induced fibrosarcoma and NFSa fibrosarcoma, were investigated using the subrenal capsule assay. Subrenal tumor growth was histologically confirmed. Volume regression and regrowth of subrenal capsule‐implanted and subcutaneously implanted tumors after X‐irradiation were compared. No difference was found in tumor growth speed (volume doubling time: 1.2–1.3 days) between the subrenal transplants into C3H/He mice, syngeneic to the tumor grafts, and those into immuno‐incompetent C57BL mice, allogeneic to the tumor grafts. The tumor growth rates for subrenal capsule transplants were 1.7‐ to 1,8‐fold higher than those for subcutaneous transplants of the same tumor type. A marked difference was found in the radiation responses of the two tumor types by the subrenal capsule assay, i.e., tumor regrowth time following 20 Gy irradiation was more than 8 days for MCA‐induced fibsarcoma and 4.5–5.4 days for radioresistant NFSa fibrosarcoma. These values correlate well with the estimated radiation sensitivities of these tumors.