LACK OF GENERAL CORRELATION BETWEEN INTERSTITIAL FLUID PRESSURE AND OXYGEN PARTIAL-PRESSURE IN SOLID TUMORS

Several studies have shown a decrease in blood perfusion and oxygen pa rtial pressure (pO(2)), and an increase in interstitial fluid pressure (IFP) with increasing tumor size. However, it is not evident if the e levated IFP is a key parameter responsible for the poor perfusion and oxygenation of solid tumors. To this end, IFP and pO(2) were measured in nine human tumor xenografts in immunodeficient mice at a fixed tumo r size (similar to 250 mm(3)). IFP and pO(2) were also measured as a f unction of tumor volume in one human colon adenocarcinoma (LS174T) and in one human glioblastoma (HGL-9). In LS174T tumors IFP did not vary with size (P < 0.7); however, median pO(2) decreased from similar to 3 5 mm Hg in 100-mm(3) tumors to similar to 15 mm Hg in tumors of simila r to 500 mm(3) (P < 0.001). In HGL-9 tumors an inverse correlation bet ween IFP and pO(2) was found; IFP increased (P < 0.001) and pO(2) decr eased (P < 0.001) with increasing tumor size. At a fixed tumor size of 250 mm(3) no correlation was found between mean IFP and median pO(2) (P < 0.5) or between the mean IFP and the hypoxic fraction PO2 < 2.5 m m Hg) (P < 0.7) in the nine tumors studied. The absence of a general r elationship between IFP and pO(2) could result in part from difference s in vascular resistance between tumors. For example, a high geometric resistance to blood flow on the arterial side will lead to a low IFP and blood flow, whereas an elevation of the venous resistance will red uce blood flow and increase IFP. In conclusion, our results show that there is no general relationship between IFP and oxygen levels in soli d tumors. (C) 1995 Academic Press, Inc.