[Changes in tumor transvascular pressure difference associated with tumor growth: implications for...

In order to further elucidate the mechanism of drug delivery to tumor tissue, changes in tumor vessel pressure and interstitial fluid pressure associated with tumor growth were measured by means of a compression method and a micro-occlusion method and a diffusion chamber method, respectively. Tumor interstitial fluid pressure was always positive and much higher than that in the normal subcutis. Furthermore the pressure became higher as the tumor mass grew. Conversely, tumor vessel pressure was reduced with tumor growth. Increase in the interstitial fluid pressure and slight decrease in the tumor vessel pressure should together result in a reduction of the hydrostatic pressure difference between the intravascular and extravascular space of the tumor, which seems to be one of the important factors influencing fluid exchange and drug delivery. However, the transvascular pressure gradient in the tumor was increased under angiotensin-induced hypertension, resulting in advantageous conditions for drug delivery.