Interstitial fluid pressure in cervical cancer: guide to targeted therapy.

Interstitial fluid pressure (IFP) is elevated in most malignant tumors, mainly as a result of the abnormal tumor vasculature that develops from unregulated angiogenesis. Theoretical models predict that IFP should correlate with capillary flow resistance in tumors, and therefore also with perfusion and oxygenation. However, a prospective clinical study in patients with cervical cancer at Princess Margaret Hospital failed to demonstrate a relationship between IFP and oxygenation. Despite this, high IFP was strongly associated with inferior survival after radiotherapy independent of clinical prognostic factors and tumor oxygen status. This suggests that IFP and direct needle oxygen measurements may provide information about different aspects of tumor oxygenation, such as chronic versus intermittent hypoxia. Alternatively, IFP may reflect an aspect of tumor biology that is largely unrelated to perfusion and oxygenation. One possibility is that tumors with high pretreatment angiogenesis levels, as indicated by high IFP, may be more radioresistant because the vascular endothelium is more likely to survive during and after treatment. The mechanistic link between elevated IFP and the abnormal tumor vasculature and the strong prognostic effect of IFP in our cervix study together suggest that drugs targeted at angiogenesis, when combined with radiotherapy, may lead to improved tumor control and patient survival.