Oxygenation status of a transplantable tumor during fractionated radiation therapy
article
Radiation survival studies are reported for cells from a transplantable solid tumor, sarcoma KHT, in C3H/Km mice. Cells from the tumor were brought into suspension and survival was determined by an endpoint-dilution method. The parameters of the X-ray survival curves for irradiation in vitro in oxygen were D0 = 115 rad, N = 10.9, and for irradiation in nitrogen D0 = 357 rad, N = 2.7. The tumor in situ was irradiated in the living animal breathing air and in the dead mouse killed with nitrogen to obtain complete anoxia. The terminal slopes of the dose-survival curves were approximately parallel and it is concluded that the tumor in vivo contains anoxic cells. The fraction of anoxic cells of the tumor in the living mouse was calculated from the distance between the parallel terminal slopes. In tumors that received no previous irradiation, on the average 14% of the cells were anoxic, and for 2 types of pretreatment with 4 or 5 times 190 rad at daily intervals this fraction was 14 and 18%, respectively. These results demonstrate that under fractionated radiotherapy, which is expected to eliminate preferentially the well-oxygenated cells from the tumor, a continuous movement of previously anoxic cells into the compartment of well-oxygenated cells must occur. The implications of these findings are discussed.
TNO Identifier
354974
Source
Journal of the National Cancer Institute, 40(3), pp. 441-451.
Pages
441-451
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