[Analysis of tumor curability in terms of cellular radiosensitivity and its application to physico-chemical therapy modes].
Analysis of curability of multicellular spheroids (a model of solid tumor) in terms of cellular radiosensitivity showed that radiosensitivity of spheroids is determined by four factors; total cell number, two parameters (mean lethal dose and extrapolation number) of cellular radiosensitivity and critical cell number. For example, an increase of cell number and two parameters make spheroids more radioresistant, while an increase of critical cell number makes them more radiosensitive. Various therapy modes could be analyzed by this analysis: Increased radioresistant of larger tumors could be attributed mostly to increased cell number and increased cellular radiosensitivity. Radiosensitization by fast neutrons could be due to increased radiosensitivity of composite cells. Hyperthermia showed a critical cell number below 1, indicating a killing mechanism different from X-rays. One of the future areas to be explored for better therapy mode could be how to increase the critical cell number through modification of environmental conditions (e.g., making the irradiated cells more able to survive or easy to die.)
Okada
S
S
Radiation Biology Center, Kyoto University.
D002452:Cell Count; D002455:Cell Division / Q000528:radiation effects; D002470:Cell Survival / Q000528:radiation effects; D005214:Fast Neutrons / Q000627:therapeutic use; D006801:Humans; D006979:Hyperthermia, Induced; D008545:Melanoma / Q000473:pathology; D008954:Models, Biological; D009369:Neoplasms / Q000188:drug therapy / Q000532:radiotherapy* / Q000628:therapy; D011836:Radiation Tolerance; D011879:Radiotherapy Dosage; D014407:Tumor Cells, Cultured / Q000473:pathology / Q000528:radiation effects