The effect of two fractions of radiation, delivered in air or in hyperbaric oxygen, on the Fib/T tumour in WHT mice pretreated with a hypoxic gas mixture.

Abstract

The response of the Fib/T tumour to equal fractions of radiation, spaced by an interval of 24 hours, was determined in tumour-bearing mice that were pretreated either with 8% oxygen for 48 h or with air. An increase in tumour cell kill occurred in the group of animals that received a low oxygen pretreatment. Tumour cell kill was further and significantly increased if mice were retained in the low oxygen environment for the 24-h interval between radiation fractions. Possible explanations for these findings are proposed and discussed. The effect of a 48 h 8% oxygen exposure in modifying the response of the Fib/T tumour to two fractions of radiation, both delivered in hyperbaric oxygen, was also investigated. The low oxygen pretreatment did not significantly alter the tumour response to radiation given under conditions of hyperbaric oxygenation.