Refining the target area in diffuse gliomas for radiation oncology based upon the location of cingulate gyrus tumors.

Abstract

e13051 Background: Glioblastoma is a brain tumor with poor survival. Radiation therapy (RTX) is often not effective and the target volume could be improved. The aim of this study is to determine if the patterns of spread for cingulate region gliomas could be used to make rational decision for safely altering the treatment planning target volume. Methods: 69 pts. with cingulate gliomas were collected from the collaborating institutions and the patterns of spread were analyzed by serial MRI evaluation. Results: Most pts. present with seizures, one ischemic stroke and one acute hemorrhage was noted. Anterior cingulate was involved in 49 pts. The basal frontal lobe (orbitofrontal or gyrus rectus) was involved in 6 pts. and the insula in 1. There were 20 cases of posterior cingulate involvement including 1 case which wrapped posteriorly from the hippocampus to indusium griseum. None of the cases spread between the anterior and posterior cingulate. 4 had bilateral cingulate involvement. Given that the callosal fibers surround but do not enter the cingulate, the postoperative imaging were assessed which showed that often the callosum was thin and edematous, or had tumor herniate through the callosal isthmus (3 cases), rather than true callosal involvement. Additional cases outside of the 69 pts. showed callosal tumors sparing the cingulate and supra-cingulate frontal and parietal tumors which did not invade the cingulate sulcus. Conclusions: For RTX the areas of cingulate tumor spread which should be considered is the adjacent corpus callosum. There appear to be a relative functional border by the cingulate sulcus and also separating the anterior and posterior cingulate at the level of the paracentral lobules, suggesting the potential for dose deescalation, which may also help with avoiding the supra-cingulate supplemental motor area and leg motor fibers. Other areas to include are the opposite cingulate gyrus, head of the caudate nucleus and septum pellucidum. Anterior cingulate lesions near the genu should include the subcallosal (risky for deficit) and ipsilateral frontal basal areas (risks for frontal lobe syndrome). Sparing the major callosal marginal or pericallosal arteries may help to avoid stroke.