HYPOXYRADIOTHERAPY - LACK OF EXPERIMENTAL-EVIDENCE FOR A PREFERENTIALRADIOPROTECTIVE EFFECT ON NORMAL VERSUS TUMOR-TISSUE AS SHOWN BY DIRECT OXYGENATION MEASUREMENTS IN EXPERIMENTAL SARCOMAS
Dk. Kelleher et al., HYPOXYRADIOTHERAPY - LACK OF EXPERIMENTAL-EVIDENCE FOR A PREFERENTIALRADIOPROTECTIVE EFFECT ON NORMAL VERSUS TUMOR-TISSUE AS SHOWN BY DIRECT OXYGENATION MEASUREMENTS IN EXPERIMENTAL SARCOMAS, Radiotherapy and oncology, 45(2), 1997, pp. 191-197
Aim: In order to investigate possible pathophysiological mechanisms un
derlying the postulated preferential protective effect of hypoxia on n
ormal tissue during radiotherapy, the impact of acute respiratory hypo
xia (8.2% O-2 + 91.8% N-2) on tissue oxygenation was assessed. Methods
: Tumor and normal tissue oxygenation was directly determined using O-
2-sensitive electrodes in two experimental rat tumors (DS and Yoshida
sarcomas) and in the normal subcutis of the hind foot dorsum. Results:
During respiratory hypoxia, arterial blood O-2 tension (pO(2)), oxyhe
moglobin saturation and mean arterial blood pressure decreased. Change
s in the arterial blood gas status were accompanied by a reflex hyperv
entilation leading to hypocapnia and respiratory alkalosis. In the sub
cutis, tissue oxygenation worsened during acute hypoxia, with decrease
s in the mean and median pO(2). Significant increases in the hypoxic f
ractions were, however, not seen. In tumor tissues, oxygenation also w
orsened upon hypoxic hypoxia with significant decreases in the mean an
d median pO(2) and increases in the size of the hypoxic fractions for
both sarcomas. Conclusion: These results suggest that during respirato
ry hypoxia, radiobiologically relevant reductions in the oxygenation (
and a subsequent selective radioprotection) of normal tissue may not b
e achieved. In addition, in the tumor models studied, a worsening of t
umor oxygenation was seen which could result in an increased radioresi
stance. (C) 1997 Elsevier Science Ireland Ltd.