Imaging responses to anti-angiogenic cancer therapy

Vessel architectural imaging (VAI) can be used in patients with glioblastoma-a type of brain tumor-to show improved microcirculation and tissue oxygenation in response to anti-angiogenic therapies. This technique, reported this week in Nature Medicine, can be used to identify those patients who respond to such therapies, as it allows for non-invasive observation of drug effects in tumor blood vessels and the surrounding tissue, which correlates to patient survival.

Imaging brain tissue using magnetic resonance imaging (MRI) provides information about tissue perfusion, blood volume and vessel caliber. Kyrre Emblem and colleagues develop the VAI technique that provides information about vessel anatomy and function, such as blood flow and tissue oxygen saturation, which cannot be easily assessed with current non-invasive imaging techniques. Using computational simulations, the authors show that vessels loops identified with VAI indicate a particular vessel architecture. They also validate the approach in the clinic using a retrospective analysis of 30 patients with recurrent glioblastoma multiforme before and after treatment with the angiogenic inhibitor cediranib, which inhibits a key protein receptor for vasculature growth.

The authors found that reduced vessel calibers correlated with improved microcirculation and oxygen saturation in patients who responded to anti-angiogenic therapy and who ultimately survived longer. They could identify a larger group of responding patients using the VAI approach, suggesting this technique may be a more sensitive biomarker than traditional MRI biomarkers for angiogenic inhibitor efficacy, in part probably because of the sensitivity of VAI to changes in oxygen saturation levels.