Correlations between radiocurability and kinetic parameters were investigated in tour transplantable tumor types in WHT/Ht mice. The radiation dose to achieve 50% tumor control at 120 days after irradiation, i.e., TCD50/120, was 30 Gy for squamous cell carcinoma H, 32 Gy for squamous cell carcinoma NOS, 46 Gy for rhabdomyosarcoma KAS, and 63 Gy for fibrosarcoma YAS. The tumor cell kinetic parameters investigated were specific growth delay, volume doubling time, 125I-iododeoxyuridine (IUdR) uptake rate, and specific cell loss rate. The specific cell loss rate was defined as the ratio of cell loss rate in non-irradiated tumors to the rate in irradiated tumors, and was obtained by measuring the retention rate of radioactivity in the tumors. No correlations were found between specific growth delay, volume doubling time, 125I-IUdR uptake rate, andTCD50. However, the specific cell loss rate correlated with the TCD50. Therefore, the 125I-IUdR labeling method may be useful as an in situ predictive assay for tumor radiocurability.
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