A standard dose (0.2 mc.) of radioactive yttrium (Y90) was injected in eight or ten fractions into peritumoral subcutaneous tissue of mice bearing Sarcoma 180 or Sarcoma 37 on the abdomen, leg, or scalp. Twelve to 48 hours after tissue infiltration, autoradiographs and Geiger counts were taken.
Tumor tissue showed a consistently higher level of radioactivity than adjacent muscle and the liver; radioactivity was low in the spleen and insignificant in other organs.
Requisite numbers (about 107) of sarcoma cells were inoculated subcutaneously into the abdominal wall or into the scalp: 1–5 days later, the tissue surrounding the site of inoculation was infiltrated (as above) with Y90 (graded doses of 0.1 to 0.35 mc. in various series). It was found that in the majority of mice treated with doses of 0.2 mc. or higher 2 days after inoculation, the tumor growth was scanty (nodules only) or absent, and the survival was longer (often indefinite) as compared with untreated controls.
It is concluded that peritoneal treatment of large tumors affects (through necrosis) consistently only their periphery, but malignant cells scattered in normal tissue can be easily reached and inactivated by infiltrated Y90 before the tumor becomes organized.
It is suggested that, in clinical therapy, infiltration of the tumor bed and tumor periphery with Y90 may arrest the peripheral growth of the tumor and may prevent the spread into normal tissue of scattered malignant cells from the tumor or of malignant cells “spilled” during surgical intervention.
This investigation was supported by grants from the National Cancer Institute, National Institutes of Health, U.S. Public Health Service; a grant from the Division of Biology and Medicine, U.S. Atomic Energy Commission; and a grant-in-aid from the American Cancer Society upon recommendation of the Committee on Growth of the National Research Council.