TABLE 1.

Comparison of PTV coverage for different studies that evaluated dose homogeneity and conformity for VMAT plans vs IMRT plans

Study (reference)	Dose fractionation	Coverage of PTV	Observations
VMAT vs IMRT for carcinomas of the oro‐pharynx, larynx hypopharynx 29 patients, (Vanetti, 2009) 19	SIB: 66 Gy, 60 Gy, 54 Gy/30 fr	Degree of plan conformality measured with a Conformity Index; Slight improvement in target dose homogeneity and coverage with VMAT	Difficult to control all sources of bias influencing plan results such as optimization performed by different planners and institutes
Single and double arc VMAT vs conventional IMRT 12 patients (Verbakel, 2009) 26	SIB: 70 Gy; 57.7 Gy/35 fr	CI for IMRT plans were 1.14 for PTVboost and 1.54 PTVelective CI for single arc were 1.21 for PTVboost and 1.60 for PTVelective CI for double arc were 1.24 for PTVboost and 1.59 for PTVelective The dose homogeneity to PTVboost was largely improved by the double arc VMAT compared with the single‐arc one	Fewer objectives for OAR used for RapidArc optimizations vs IMRT. No objectives for oral cavity, larynx, upper back of the neck, lower back of the neck, brain, or lungs; all replaced by a simple ring structure around the PTV and the normal tissue objective in the optimizer
Single arc volumetric modulated arc therapy of HNC 25 patients (Bertelsen, 2010) 27	SIB: 68/66 Gy, 60 Gy, 50 Gy/33 fr	CI for PTV50: IMRT: 1.65 and VMAT: 1.57 CI for PTV60: IMRT: 1.66 and VMAT: 1.59 CI for PTV66/68: IMRT: 1.71 and VMAT: 1.69	All plans were forced to use only one single arc
VMAT and step‐and‐shoot IMRT in head and neck Cancer 15 patients (Wiehle, 2011) 4	70 Gy, 60 Gy, and 50 Gy/total of 35 fr	QI average VMAT: 36.3 and IMRT: 66.5 CVF [95%] average for VMAT: 0.09 and IMRT:0.25 CVF [80%] average for VMAT 0.45 and IMRT: 0.87	Comparison between different planning systems and linacs. Only treatment plans for PTV1 (encompassed draining lymph nodes) were considered in this study.
VMAT vs IMRT SiB of nasopharyngeal Carcinomas 20 patients (Lee, 2011) 9	SIB: 70 Gy 59.4 Gy, 54 Gy Gy/33 fr	For all target volumes, CI was higher for VMAT, and in some case was equal with CI of IMRT There is no significant difference between VMAT and IMRT	Bias minimized by cross‐planning by two equally experienced planners and dose protocols approved by an oncologist specialized in nasopharyngeal carcinomas
VMAT vs TomoTherapy vs step‐and‐shoot IMRT 20 patients (Lu, 2011) 10	SIB: 70 Gy; 60 Gy; 54 Gy/33 fr	Plans compared with conformity index (CI), homogeneity index (HI) Both CI and HI were higher for IMRT	Limitation: the use of a coplanar beam for VMAT/IMRT planning. For VMAT parameter settings affects planning quality (collimator angles, arc numbers, rotation angles, use of noncoplanar beam).
Smartarc‐based VMAT vs IMRT vs tomotherapy 8 patients (Clemente, 2011) 11	SIB: 70 Gy; 63 Gy; 58.1 Gy/35 fr	Average CI for VMAT: 1.5 Average CI for IMRT: 1.6	Limited number of patients
A comparison of several modulated RT techniques 10 patients (Stieler, 2011) 12	60 Gy for PTVhigh 56 Gy for PTVlow	Average CI for VMAT: 1.82 Average CI for IMRT: 2.23 HI for VMAT for PTVhigh 1.20 HI for VMAT for PTVhigh 1.11	Limited number of patients
Clinical experience transitioning from IMRT to VMAT for HNC 20 patients (Studenski, 2012) 15	All cases were rescaled to a dose of 70 Gy in 2 Gy fractions for consistency in the comparison.	VMAT provides comparable coverage of target volumes to IMRT	No specific comparison for target volumes coverage. IMRT optimizer Elekta XIO v4.62 and VMAT optimizer Nucletron Oncentra MasterPlan v4.1
VMAT vs conventional intensity modulated radiation therapy 20 patients (Fung‐Kee‐Fung, 2012) 2	For patients with unresected tumor: SIB 70 Gy/66–60 Gy/56 Gy in 35 fractions For patients receiving post‐operative radiation: SIB 66 Gy/56 Gy	Plans were compared for dose conformity and homogeneity VMAT plans trended towards better dose homogeneity but ultimately were found to have statistically significant less conformity in PTV irradiation compared to IMRT plans.	Optimization and dose calculations performed with Eclipse version 8.1 for IMRT. VMAT planning performed in Eclipse version 8.5, using the AAA calculation algorithm, and the Progressive Resolution optimization algorithm
Static and rotational intensity modulated techniques for HNC 18 patients (Broggi, 2014) 13	SIB 66 Gy/54 Gy/30 fr	For IMRT homogeneity of PTVhigh 1.12 and for PTVlow was 1.21 For VMAT (Eclipse) homogeneity of PTVhigh 1.12 and for PTVlow was 1.20; For RapidArc (Varian) homogeneity of PTVhigh 1.11 and for PTVlow was 1.19	Dosimetric differences due to variations among various optimization/objective function/leaf sequencing approaches used in different planning systems.
Equally spaced beam, beam angle optimization, and VMAT in HNC 119 patients (Leung, 2019) 17	66–70 Gy for high‐risk PTV/60 Gy for intermediate risk PTV/54 Gy for low‐risk PTV	For the target volumes the dose parameters were the homogeneity index (HI) and conformation number (CN). HI was lower for both VMAT plans CN was higher for both VMAT plans	Five hypothetical plans computed for each patient using the Eclipse treatment planning system Version 13.6 by the same dosimetrist, significantly reducing bias.
VMAT, IMRT and helical tomotherapy for the ESCALOX‐trial pre‐study 6 patients (Pigorsch, 2020) 7	SIB: 77 Gy, 70 Gy, 56 Gy/35 fr	CVF was equal for IMRT and VMAT for PTV77 and PTV56, while it was higher for IMRT for PTV70; CN was higher in IMRT for PTV77 and PTV56 and higher for VMAT for PTV70; HI was equal for PTV77 and higher for VMAT for PTV70 and PTV56	Limited number of patients

Abbreviations: CI, conformity index; CN, conformation number; CVF, coverage factor; fr, fractions; HI, homogeneity index; HNC, head and neck cancer; IMRT, intensity modulated radiation therapy; PTV, planning target volume; QI, quality index; RT, radiotherapy; SIB, simultaneous integrated boost; VMAT, volumetric modulated arc therapy.