[Linac-based stereotactic ablative radiotherapy for pancreatic cancer with intrafractional triggered imaging]

Our aim was to present different treatment strategies (non-gated [NG], respiratory-gated [RG] and deep inspiration breath-hold [DIBH] technique) of linac-based stereotaxic ablative radiotherapy (SABR) for pancreatic cancer in terms of use of marker, abdominal compression, image quality, and time efficiency. From October 2016 to October 2020 14 patients were treated with VMAT-based SABR (NG: 6/14, 8/14 RG RT including 3/8 DIBH SABR). Treatment verification consisted of 3D/4D CBCTs. For intrafractional tumor visualization (11/14) different type of fiducials were used. The average treatment time was the shortest with NG RT, followed by DIBH and RG RT. However, the best image quality was achieved with DIBH technique. The Krippendorff's agreement test among three independent RTTs showed that DIBH CBCT (Cone Beam CT) can produce sufficient image quality for OARs and can be used to reliably determine OARs position related to safety zone (PRV). Overall, marker-based DIBH SABR with intrafractional tumor visualization appears to be the best technique on linac at present.