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Fractionated dose of 35‐MeV fast neutrons and hypoxic tumor cell survival curve
Author(s) -
U Raymond,
Evans John C.,
Cavanaugh Patrick J.,
Abramson Norman,
Thompson Thomas T.,
Wheless Don M.
Publication year - 1975
Publication title -
cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.052
H-Index - 304
eISSN - 1097-0142
pISSN - 0008-543X
DOI - 10.1002/1097-0142(197506)35:6<1658::aid-cncr2820350627>3.0.co;2-s
Subject(s) - nuclear medicine , population , irradiation , neutron temperature , medicine , in vivo , neutron , radiobiology , radiochemistry , radiation therapy , chemistry , biology , physics , nuclear physics , genetics , environmental health
The determination of the RBE for the MANTA fast neutrons produced by NRL is in progress, with the model system using tumor cell population kinetic response patterns assayed in vitro after irradiation in vivo. Ascites tumor cells BW‐5147 were irradiated with a clinically usable fast neutron beam from the NRL cyclotron, which is produced by accelerating deuterons to 35 MeV and using them to bombard a thick beryllium target. The comparison of dose‐effect relationships was made for doses ranging from 30 to 1000 rads. The doses required for an isoeffect on BW‐5147 hypoxic tumor cell survival and impairment of its reproductive capacity from fast neutron exposure were not different whether it was given in a single dose or the same dose given in three fractions separated by long recovery periods in situ. No intracellular repair of sublethal injury of hypoxic cells was demonstrated with fast neutrons. The reference experiments with 250‐kVp x rays, however, showed a considerable repair of sublethal injury when the dose was given in three fractions, although the hypoxic BW‐5147 tumor cells have no effective reoxygenation or repopulation in this time interval. The RBE for the fast neutron beam is 4 relative to x rays for fractionated doses at the surviving fraction level of 0.6–0.7, while the RBE is 2.5 for single doses. However, at a surviving fraction of 0.1, the RBE is 1.9 for single and 2.8 for fractionated doses. Analysis of the daily cell population kinetic patterns showed that there was no difference for repopulation rate or mitotic delay between the two types of radiations at a similar level of survival.