Review of. cap alpha. /. beta. ratios for experimental tumors: implications for clinical studies of altered fractionation

Journal Article · Tue Jan 01 04:00:00 EST 1985 · Int. J. Radiat. Oncol., Biol. Phys.; (United States)

DOI:https://doi.org/10.1016/0360-3016(85)90366-9· OSTI ID:5751664

Williams, M V; Denekamp, J; Fowler, J F

Clinical interest in the use of more and smaller dose fractions in radical radiotherapy has been stimulated by recent reviews of experimental results with normal tissues. It has been found that if the dose per fraction is reduced (i.e., in hyperfractionation) there is sparing of late responding normal tissues relative to those which respond early. This phenomenon can be understood in terms of the shapes of the underlying dose effect relationships, which can be described using the linear quadratic equation. The ratio (..cap alpha../..beta..) of the linear (..cap alpha..) and quadratic (..beta..) terms is a useful measure of the curviness of such dose effect curves. The authors have reviewed published results for experimental tumors irradiated in situ and either assayed in situ or after excision. The ..cap alpha../..beta.. ratios were usually at least as high as those for acutely responding normal tissues, and 36/48 tumors gave values > 8 Gy. Low values of less than 5 Gy were obtained for only 4/48 tumors. There are considerable technical problems in interpreting these experiments, but the results do suggest that hyperfractionation might confer therapeutic gain relative to late responding normal tissues on the basis of differences in repair capability. In clinical practice more efficient reoxygenation, cell cycle redistribution and decreased overall treatment time might also confer therapeutic gain.

• Research Organization: Mount Vernon Hospital, Northwood, England
• OSTI ID: 5751664
• Journal Information: Int. J. Radiat. Oncol., Biol. Phys.; (United States), Journal Name: Int. J. Radiat. Oncol., Biol. Phys.; (United States) Vol. 11:1; ISSN IOBPD
• Country of Publication: United States
• Language: English

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62 RADIOLOGY AND NUCLEAR MEDICINE
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ANIMAL TISSUES
BIOLOGICAL RECOVERY
BIOLOGICAL REPAIR
BODY
CELL CYCLE
DOSE-RESPONSE RELATIONSHIPS
DOSES
EXPERIMENTAL NEOPLASMS
FRACTIONATED IRRADIATION
IN VITRO
IN VIVO
IRRADIATION
MEDICINE
NUCLEAR MEDICINE
RADIATION DOSES
RADIOLOGY
RADIOSENSITIVITY
RADIOSENSITIVITY EFFECTS
RADIOTHERAPY
RECOVERY
REPAIR
SIDE EFFECTS
THERAPY
TISSUES