Dosimetric comparison between Intensity Modulated Radiation Therapy (IMRT) vs dual arc Volumetric Arc Therapy (VMAT) for nasopharyngeal cancer (NPC): Systematic review and meta-analysis

Abstract

Background and PurposePrevious non-randomised studies comparing dosimetric outcomes between advanced techniques such as IMRT and VMAT reported conflicting findings. We thus sought to perform a systematic review and meta-analysis to consolidate the findings of these studies. Materials and MethodsWe searched PUBMED and EMBASE for eligible studies from their time of inception to 10 March 2022. A random effects model was used to estimate the pooled mean differences (MDs) and their 95% confidence intervals(CIs) for target volume coverage, organ-at-risk(OAR) doses, monitor units(MUs) and treatment delivery times. We also performed a subgroup analysis to evaluate if different treatment planning systems (TPS) (Eclipse, Monaco and Pinnacle) used affected the pooled mean differences. ResultsA total of 17 studies (383 patients) were eligible to be included. The pooled results showed that dual arc VMAT reduced D2% of PTV (MD=0.71Gy,95%CI=0.14-1.27,P=0.01), mean left cochlea dose (MD=2.6Gy,95%CI=0.03-5.16,P=0.05), mean right cochlea dose (MD=3.4Gy,95%CI=0.7-6.1,P=0.01), MUs (MD=554.9,95%CI=245.8-863.9,P=0.0004), treatment delivery times (MD=6.7mins,95%CI=4.5-8.9,P<0.0001) and integral dose (MD=0.97Gy,95%CI=0.28-1.67,P=0.006). None of the other indices were significantly better for the IMRT plans.The subgroup analysis showed that the integral dose was significantly lower only for Eclipse (MD=0.88Gy, 95%CI=0.14-1.63, P=0.02). The total MUs was significantly lower only for Eclipse (MD=1035.2, 95%CI=624.6-1445.9, P<0.0001) and Pinnacle (MD=293, 95%CI=15.6-570.5, P=0.04). Similarly, delivery time was also significantly lower only for Eclipse (MD=6.1mins, 95%CI=5.7-6.5, P<0.0001) and Pinnacle (MD=4.9mins, 95%CI=2.6-7.2, P<0.0001). The subgroup analysis however showed that target coverage was superior for the IMRT plans for both Pinnacle (MD=0.48Gy, 95%CI=0.31-0.66, P<0.0001) and Monaco (MD=0.12Gy, 95%CI=0.07-0.17, P<0.0001). ConclusionDual-arc VMAT plans improved OAR doses, MUs and treatment times as compared to IMRT plans. The different TPS used may modify dosimetric outcomes.