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Yucel Saglam,1,2 Yasemin Bolukbasi,1– 3 Ali Ihsan Atasoy,1 Fatih Karakose,1 Mustafa Budak,1 Vildan Alpan,1,2 Erkan Topkan,4 Ugur Selek1– 3 1Koc University, School of Medicine, Department of Radiation Oncology, Istanbul, Turkey; 2UT MD Anderson Radiation Oncology Outreach Center at American Hospital, Istanbul, Turkey; 3University of Texas, MD Anderson Cancer Center, Department of Radiation Oncology, Houston, TX, USA; 4Baskent University Medical Faculty, Department of Radiation Oncology, Adana, TurkeyCorrespondence: Ugur SelekKoc University, School of Medicine, Department of Radiation Oncology, Davutpasa Caddesi, No: 4, 34010, Topkapi, Istanbul, TurkeyEmail ugurselek@yahoo.comPurpose: To evaluate the feasibility of shortening the duration of liver stereotactic radiotherapy (SBRT) without jeopardizing dosimetry or conformity by utilizing weight-optimized dynamic conformal arcs (WO-DCA) as opposed to volumetric modulated arc therapy (VMAT) for tumors away from critical structures.Methods: Nineteen patients with liver metastasis were included, previously treated with 50 Gy in 4 fractions with VMAT technique using two partial coplanar arcs of 6 MV beams delivered in high-definition multi-leaf collimator (HD-MLC). Two coplanar partial WO-DCA were generated on Pinnacle treatment planning system (TPS) for each patient; and MLC aperture around the planning target volume (PTV) was automatically generated at different margins for both arcs and maintained dynamically around the target during arc rotation. Weight of the two arcs using optimization method was adjusted between the arcs to maximize tumor coverage and protect organs at risk (OAR) based on the RTOG‐0438 protocol.Results: The WO-DCA plans successfully “agreed” with the standard VMAT for OAR (liver, spinal cord, stomach, duodenum, small bowel, and heart) and PTV (Dmean, D98%, D2%, CI, and GI), with superior mean quality assurance (QA) pass rate (97.06 vs 93.00 for VMAT; P < 0.001 and t = 8.87). Similarly, the WO-DCA technique additionally reduced the beam‐on time (3.26 vs 4.43; P < 0.001) and monitor unit (1860 vs 2705 for VMAT; P < 0.001) values significantly.Conclusion: The WO‐DCA plans might minimize small‐field dosimetry errors and defeat patient‐specific VMAT QA requirements due to the omission of MLC beam modulation through the target volume. The WO‐DCA plans may additionally enable faster treatment delivery times and lower OAR without sacrificing target doses in SBRT of liver tumors away from critical structures.Keywords: liver, stereotactic body radiotherapy, dynamic conformal arcs, weight optimization, VMAT |
