Neutron radiobiology revisited.
The present paper reviews the experimental results of normal tissue and tumour studies in animals. The dose per fraction dependence of the RBE in normal tissues has been long recognised, together with the steeper increase of RBE at low doses for late responding tissues compared with acute reactions. The dose dependence for tumours is more complex, because of hypoxia and reoxygenation, as well as differences in repair capability after high LET damage. A comparison of tumour and normal tissue RBE values shows that there is little experimental evidence for a therapeutic advantage at clinically relevant doses. In particular, the RBE for slow growing tumours is even lower than that for the faster growing mouse tumours. The reasons for the loss of expected neutron benefits in clinically relevant experiments are discussed. The disappointing prospects for neutrons are contrasted with the current multifactorial approaches to overcoming resistance to more conventional low LET radiations, including acceleration, hyperfractionation and several types of hypoxic cell radiosensitizers.
CRC Gray Laboratory, Mount Vernon Hospital, Northwood, Middlesex, England.
J
J
Denekamp
D000818:Animals; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D009369:Neoplasms / Q000532:radiotherapy*; D009502:Neutrons / Q000627:therapeutic use*; D011838:Radiation-Sensitizing Agents / Q000627:therapeutic use; D011853:Radiobiology; D011879:Radiotherapy Dosage
D011838:Radiation-Sensitizing Agents