The influence of radiation dose on the magnitude and kinetics of reoxygenation in a C3H mammary carcinoma.
The variation in hypoxic fraction as a function of time after various priming doses of radiation has been investigated in a C3H mouse mammary carcinoma in situ. The hypoxic fraction was calculated from data for local tumor control. Untreated tumors were found to contain 4.8% radiobiologically hypoxic cells. Within minutes after a priming dose of 20 Gy given in air, the hypoxic fraction increased to a value not significantly different from 100%. After 4 h, reoxygenation was complete (hypoxic fraction 1.3%), and the hypoxic fraction stabilized at a level significantly below the untreated value. Following a priming dose of 40 Gy the reoxygenation pattern was different: The hypoxic fraction stayed above the pretreatment value for 4 h, and pronounced reoxygenation occurred after 12 h (hypoxic fraction 0.4%). At longer time intervals the hypoxic fraction again increased to--and slightly above--the oxygenation level of untreated tumors. The present findings show that reoxygenation in solid tumors is a function of radiation dose, and the data suggest that mechanisms other than a decrease in tumor cell O2 consumption are involved in tumor reoxygenation.
Grau
C
C
Department of Experimental Clinical Oncology, Radiumstationen, Aarhus C, Denmark.
Overgaard
J
J
D000818:Animals; D015687:Cell Hypoxia / Q000502:physiology / Q000528:radiation effects*; D008297:Male; D008325:Mammary Neoplasms, Experimental / Q000503:physiopathology / Q000532:radiotherapy*; D051379:Mice; D009368:Neoplasm Transplantation; D011879:Radiotherapy Dosage; D013997:Time Factors