A simple, yet novel hybrid‐dynamic conformal arc therapy planning via flattening filter‐free beam for lung stereotactic body radiotherapy

Abstract

Due to multiple beamlets in the delivery of highly modulated volumetric arc therapy (VMAT) plans, dose delivery uncertainties associated with small-field dosimetry and interplay effects can be concerns in the treatment of mobile lung lesions using a single-dose of stereotactic body radiotherapy (SBRT). Herein, we describe and compare a simple, yet clinically useful, hybrid 3D-dynamic conformal arc (h-DCA) planning technique using flattening filter-free (FFF) beams to minimize these effects. Materials and Methods: Fifteen consecutive solitary early-stage I-II non-small-cell lung cancer (NSCLC) patients who underwent a single-dose of 30 Gy using 3-6 non-coplanar VMAT arcs with 6X-FFF beams in our clinic. These patients' plans were re-planned using a non-coplanar hybrid technique with 2-3 differentiallyweighted partial dynamic conformal arcs (DCA) plus 4-6 static beams. About 60-70% of the total beam weight was given to the DCA and the rest was distributed among the static beams to maximize the tumor coverage and spare the organs-atrisk (OAR). The clinical VMAT and h-DCA plans were compared via RTOG-0915 protocol for conformity and dose to OAR. Additionally, delivery efficiency, accuracy, and overall h-DCA planning time were recorded. Results: All plans met RTOG-0915 requirements. Comparison with clinical VMAT plans h-DAC gave better target coverage with a higher dose to the tumor and exhibited statistically insignificance differences in gradient index, D 2cm , gradient distance and OAR doses with the exception of maximal dose to skin (P = 0.015). For h-DCA plans, higher values of tumor heterogeneity and tumor maximum, minimum and mean doses were observed and were 10%, 2.8, 1.0, and 2.0 Gy, on average, respectively, compared to the clinical VMAT plans. Average beam on time was reduced by a factor of 1.51. Overall treatment planning time for h-DCA was about an hour. Conclusion: Due to no beam modulation through the target, h-DCA plans avoid small-field dosimetry and MLC interplay effects and resulting in enhanced target coverage by improving tumor dose (characteristic of FFF-beam). The h-DCA simplifies treatment planning and beam on time significantly compared to clinical VMAT plans. Additionally, h-DCA allows for the real time target verification and eliminates patient-specific VMAT quality assurance; potentially offering cost-effective, same or

Dynamic conformal arc radiotherapy for locally advanced lung cancer: a comparison with static-beam conformal radiotherapy

“…The hybrid static and dynamic arc plans showed better dose conformity and reduced the doses to the lung and spinal cord. Pokhrel et al compared hybrid 3D conformal arc and VMAT plans using flattering filter-tree beams in a stereotactic body radiation therapy setting for small, early- stage NSCLC [ 6 ]. They found better target coverage, higher tumor dose parameters, and a shorter overall treatment planning time for the hybrid conformal arc plan.…”

Novel Clinically Weight-Optimized Dynamic Conformal Arcs (WO-DCA) for Liver SBRT: A Comparison with Volumetric Modulated Arc Therapy (VMAT)

“…On the other hand, forward planning-based DCA delivery was shown to be efficient in lung SBRT by degrading the worries of the interplay effect. [21][22][23][24][25] The overall goal with DCA was to reduce treatment time with lower geometric complexity, which may diminish the risk of interplay errors induced by respiratory motion. As Pokhrel et al previously emphasized, flattening filter free (FFF) VMAT for SBRT of lung lesions would improve dose coverage at tumor-lung interface compared to flattened beams, 46 and additionally, there is growing evidence for FFF VMAT of various other tumor sites including the liver, brain, prostate, cervix cancers.…”

“…While lung SBRT studies have attested the necessity of using multiple arcs to obtain the average benefit for hypo-fractionated VMAT (Dynamic conformal arcs for lung stereotactic body radiation therapy: A comparison with volumetric-modulated arc therapy), an alternative technique such as dynamic conformal arcs (DCA) has been proposed to reduce or eliminate concerns of the interplay effect brought about by MLC movement in small areas. [20][21][22][23][24][25] In this respect, Pokhrel et al uncovered that hybrid 3Ddynamic conformal arc (h-DCA) therapy, a blend of the dynamic conformal arcs and static fields, in lung radiotherapy minimized the small-field dosimetry and MLC interplay effects with ensuant improved target coverage. 26 In the same way, Ross et al modified the dynamic conformal arc (MDCA) technique for lung SBRT and documented improved quality and PTV coverage with shortened treatment times in several clinical models.…”

A novel CRT‐IMRT‐combined (Co‐CRIM) planning technique for peripheral lung stereotactic body radiotherapy in pinnacle treatment planning system

“…1 , 11 , 14 Most of the existing studies focused on comparing and evaluating the pros and cons of different techniques, while there is no consensus on which technique is the best strategy for lung SBRT planning. 18 Some scholars tried to propose a hybrid planning strategy of CRT and IMRT/VMAT 6 , 19 , 20 , 21 , 22 to combine their pros while avoiding cons. The core of these hybrid methods is to add part CRT MLC modulation to VMAT/IMRT plans which require at least two kinds of fields with different techniques or multiple optimizations.…”