Experimental Studies Of Radiobiological Effects Of Carbogen Plus Low Concentration Oxygen Radiotherapy(CPLCOR)

The presence of hypoxic cells within tumors is widely regarded as one major determinant of treatment failure in patients following radical radiotherapy. Use of carbogen or oxygen breathing prior to and during radiation, to overcome tumor hypoxia, has shown some advantages in most experimental studies ,but limited to the enhancement of normal tissue injury. On the other hand, hypoxyradiotherapy which aim to protect normal tissues might have some sort of protective effect on tumor especially subclinical lesion leading to decrease of tumour response. It was known that there was transportation difference of oxygen between tumors and normal tissues. This difference had been proved by polargraphyic measurement of pO₂.which indicated that pO₂ in tumor tissue enhanced after 5minutes carbogen breathing, and will be kept on high level for at least 2minutes after switching to low concentration oxygen exposure. Meanwhile ,pO₂ in normal tissue markedly decreased right after low concentration oxygen inhalation. We conjectured that radiation be given within a time course, when the pO₂ in normal tissue was relatively lower and in tumour relatively higher, higher tumor response and lower normal tissue damage would be obtained. This approach was named "Carbogen Plus Low Concentration Oxygen Radiotherapy"(CPLCOR). A sires experiments were performed to demonstrate the effectiveness of this method.The transplantable spontaneous tumor LA-795 in inbred T-739 mice was used for tumour response studies ,and the skin reaction of hind foot of Kwunmin Mice for normal...