A novel and clinically useful weight-optimized dynamic conformal arc in stereotactic radiation therapy of non-small cell lung cancer: Dosimetric comparison of treatment plans with volumetric-modulated arc therapy

Purpose: This study constitutes a feasibility assessment of dynamic conformal arc (DCA) therapy as an alternative to volumetric-modulated arc therapy (VMAT) for stereotactic body radiation therapy (SBRT) of lung cancer with the free-breathing technique using four-dimensional computed tomography.Methods: A total of 25 patients who received 50 Gy in four fractions treated using VMAT technique having two partial coplanar arcs with 6 MV beams for non-small cell lung cancer (NSCLC) were included. Plans were re -planned using a novel and clinically technique of weight optimized based on dynamic conformal Arcs with two coplanar partial dynamic conformal arcs (WO-DCA). For the two partial arcs, MLC aperture around the 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). The clinical VMAT and WO-DCA plans were compared via the RTOG-0915 protocol for conformity and dose to the organs at risk (OAR). Additionally, delivery efficiency, quality assurance pass rate, monitor unit and beam treatment time were recorded.Results: The mean value of quality assurance (QA) pass rate 98.16 +/- 1.27 in WO-DCA and 92.87 +/- 1.56 in VMAT. The rate was higher in WO-DCA (p < 0.001 and t = 8.75). The values of beam-on time (BOT) and monitor units (MU) in the VMAT technique were 4.20 (3.45-4.95) and 3155 (2279-4867) and they were 3.10 (2.85-3.35) and 2167 (1702-2948) in WO-DCA. These values were significantly improved with WO-DCA (p < 0.001 and p < 0.001)Conclusions: As there is, no beam modulation through the target, WO-DCA plans could potentially minimize small-field dosimetry error without MLC interplay effects via respiratory motion and provide similar doses to OAR and the tumor while providing faster treatment delivery by significantly reducing MU and BOT in lung cancer for tumors of appropriate localization. Additionally, providing WO-DCA eliminate patient-specific VMAT quality assurance; potentially offering cost-effective, same day SBRT treatments.