Consensus for a postoperative atlas of sinonasal substructures from a modified Delphi study to guide radiotherapy in sinonasal malignancies.

Background: Sinonasal and skull base tumor surgery-related morbidity has been reduced by the use of endoscopic endonasal skull base surgery (EESBS). Postoperative radiation therapy (poRT) requires precise definition of target volumes. To enhance the accuracy of poRT planning, histological and radiological correlations are necessary to locate the tumor attachment on poRT CT scans. An accurate atlas of structures resected or identified during EESBS could serve for the interdisciplinary postoperative management of patients, personalizing poRT by adequate radiation dose delivery. The objective of this study was to achieve a consensual segmentation atlas on CT scan with surgeons practicing EESBS and radiation oncologists.

Methods: The sinonasal structures relevant for poRT of sinonasal malignancies were determined by a two-round Delphi process. A rating group of 25 European experts in sinonasal malignancies was set up. Consensual structures emerged and were used to determine the anatomical limits of the retained structures to draft an atlas with expert based relevant structures. The atlas was then critically reviewed, discussed, and edited by another 2 skull base surgeons and 2 radiation oncologists.

Results: After the two rating rounds, 46 structures obtained a strong agreement, 7 an agreement, 5 were rejected and 5 did not reach consensus. The atlas integrating all the selected structures is presented attached.

Conclusion: Consensual segmentation atlas on CT scan might allow, through careful poRT planning to limit the morbidity of poRT while maintaining good local control. Prospective studies are necessary to validate this potential precision medicine-based approach.