Targeted target volumes.

Top Line: Radiation plays an important role in the treatment of meningiomas, but in some locations these targets can be challenging to delineate on CT and MRI.

The Study: Almost all meningiomas express somatostatin receptor 1/2, which is a target for 68Gallium-DOTATATE PET/CT. In this study, 4 CNS radiation oncologists and 3 neuroradiologists delineated gross tumor volume (GTV) on both MRI and 68Ga-DOTATATE PET images for 25 patients with new or recurrent meningioma imaged with both modalities. Overall, PET volumes were more consistent among observers than MRI volumes. The biggest difference in target volumes was in the postoperative setting where the median GTV size was 23.2cc with MRI compared to 2.3cc with PET. This huge difference in volume was likely driven by the inclusion of surgical cavity without gross disease using MRI whereas only hypermetabolic areas were contoured on PET. With intact cases, median GTV sizes were actually slightly larger with PET than MRI (16.7cc v 15cc). Interestingly, 28% of patients had GTV contoured on PET that was not contoured on MRI and not adjacent to the primary GTV. Roughly half of these were post-op cases and the others were intact. In two patients with retrospectively generated treatment plans, PET-based target volumes resulted in significantly lower dose to organs at risk.

TBL: 68Ga-DOTATATE PET (if you can get it covered) may help delineate smaller, more precise meningioma target volumes while potentially catching sites of disease overlooked with MRI. | Perlow, Int J Radiat Oncol Biol Phys 2022