Tritium uptake, half‐lives and radiation doses in tissues of cancer patients treated with tritiated 2‐methyl‐1: 4‐naphthaquinol diphosphate

Comparisons of the uptake into tumour biopsies 30 min after intravenous or intra‐arterial injections showed that tumours of gastrointestinal origin took up significantly greater amounts of the tritiated drugs than did any other group of tumours, and with other types of tumours some individual biopsies showed very high tumour specific activities after intra‐arterial injections. The tritium in the tumour disappeared by two exponential decay processes, one with a half‐life of 1.35 days and the other with a half‐life of 14.4 days. The ratio of the concentration of the long‐lived component to that of the short‐lived component was 0.33. Tritium estimations on normal tissues taken at autopsy from patients who received only one injection of the tritiated drug showed that the biological half‐life in normal tissues ranged from 5.7 days (heart) to 34.5 days (long‐lived component in brain). The initial specific activity in μc/g for each c/kg injected ranged from 71 (long‐lived component in brain) to 505 (kidney). After a single injection of 1 c of the drug per kg body weight, the greatest doses of radiation were received by the kidney (1,600 R), testis (1,300 R), liver (1,050 R) and brain (990 R). The lowest doses were received by skeletal muscle (395 R) and bone marrow (604 R). The radiation dose in the tumour depends on the initial concentration and the half‐life in the tumour. Initial tumour concentrations of 5–8 mc/g wet tissue should give radiation doses in the therapeutic range after a single injection.