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

BACKGROUND AND PURPOSE: Previous 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 METHODS: We 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. RESULTS: A 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). CONCLUSION: Dual-arc VMAT plans improved OAR doses, MUs and treatment times as compared to IMRT plans. The different TPS used may modify dosimetric outcomes.

Implementation of temporal lobe contouring protocol in head and neck cancer radiotherapy planning: A quality improvement project.

Temporal lobe necrosis as result of radiation for nasopharyngeal cancer (NPC) occurs up to 28% of NPC patients. The only effective mitigation is by strict adherence to temporal lobe dose tolerances during radiotherapy planning, which in turn hinges on accurate temporal lobe delineation. We aim to improve the accuracy and to standardize temporal lobe contouring for patients receiving head and neck radiotherapy for NPC in a tertiary teaching hospital in Singapore.The baseline data were obtained from 10 patients in the diagnostic phase and the effect of interventions were measured in 37 patients who underwent head and neck radiotherapy over a 6-month period.We conducted the project based on the Clinical Practice Improvement Program methodology. The baseline pooled mean percentage variation in temporal lobe contouring was 39.9% (0.8%-60.2%). There was a low level of temporal lobe contouring concordance and this provided the impetus for implementation of strategies to improve the accuracy and reproducibility of temporal lobe contouring. The interventions included supervision and training of radiation therapists and residents in temporal lobe contouring, and standardization of temporal lobe contouring with a protocol and contouring atlas.Thirty-seven patients were treated during the study period from June to November 2014. Following implementation of the first set of interventions, the pooled mean percentage variation in temporal lobe contouring decreased but was not sustained. The implementation of the second set of interventions resulted in a decrease from 39.9% (January to September 2014) to 17.3% (October to November 2014) where P = .004 using t test. Weekly variation was seen throughout the study period but the decrease was sustained after standardizing and providing a contouring atlas for temporal lobe contouring.Temporal lobe contouring can be standardized through effective implementation of a temporal lobe contouring protocol and atlas.

Assessing radiation exposure of the left anterior descending artery, heart and lung in patients with left breast cancer: A dosimetric comparison between multicatheter accelerated partial breast irradiation and whole breast external beam radiotherapy.

BACKGROUND AND PURPOSE: This study aims to quantify dosimetric reduction to the left anterior descending (LAD) artery, heart and lung when comparing whole breast external beam radiotherapy (WBEBRT) with multicatheter accelerated partial breast irradiation (MCABPI) for early stage left breast cancer. MATERIALS AND METHODS: Planning CT data sets of 15 patients with left breast cancer receiving multicatheter brachytherapy post breast conserving surgery were used to create two independent treatment plans - WBEBRT prescribed to 50 Gy/25 fractions and MCABPI prescribed to 34 Gy/10 fractions. Dose parameters for (i) LAD artery, (ii) heart, and (iii) ipsilateral lung were calculated and compared between the two treatment modalities. RESULTS: After adjusting for Equivalent Dose in 2 Gy fractions(EQD2), and comparing MCAPBI with WBEBRT, the largest dose reduction was for the LAD artery whose mean dose differed by a factor of 7.7, followed by the ipsilateral lung and heart with a factor of 4.6 and 2.6 respectively. Compared to WBEBRT, the mean MCAPBI LAD was significantly lower compared to WBEBRT (6.0 Gy vs 45.9 Gy; p<0.01). Mean MCAPBI heart D(0.1cc) (representing the dose received by the most highly exposed 0.1 cc of the risk organ, i.e. the dose peak) was significantly lower (16.3 Gy vs 50.6 Gy; p<0.01). Likewise, the mean heart dose (MHD) was significantly lower (2.3 Gy vs 6.0 Gy; p<0.01). Peak dose and mean lung dose (MLD) for ipsilateral lung was also lower for MCAPBI compared to WBEBRT (Peak dose: 22.2 Gy vs 52.0 Gy; p<0.01; MLD: 2.3 Gy vs 10.7 Gy; p<0.01). CONCLUSION: Compared to WBEBRT, MCAPBI showed a significant reduction in radiation dose for the LAD, heart and lung. This may translate into better cardiac and pulmonary toxicities for patients undergoing MCAPBI.

Body mass index and patient CT measurements as a predictor of benefit of intensity-modulated radiotherapy to the supraclavicular fossa.

BACKGROUND: Irradiation of the supraclavicular fossa is commonly used as part of adjuvant breast radiotherapy. Intensity-modulated radiotherapy (IMRT) may be used to target this region accurately, and there are subgroups of patients that may benefit more from IMRT than others. We identify the benefit of IMRT over fixed-depth dose prescription to the supraclavicular fossa in patients of different builds in a clinical setting. METHODS: Fifteen patients who received radiotherapy to the left breast and supraclavicular fossa were selected. Computed tomographic planning was used to generate plans for supraclavicular fossa coverage. Dose prescription to 1.5 cm and 3.0 cm depths was compared with IMRT plans. Coverage of the planning target volume and dose to the organs at risk were compared and correlated with patient body mass index (BMI) and computed tomography measurements. RESULTS: Within the IMRT group, increasing depth of the supraclavicular fossa produced significantly better coverage of the planning target volume with IMRT. IMRT resulted in lower mean doses to the brachial plexus (P = 0.00) when compared with 1.5 cm and 3 cm depth dose prescriptions, but higher maximum brachial plexus doses. IMRT was more beneficial in patients with lower BMI because this resulted in a decreased maximum brachial plexus dose (P-values of 0.03 and 0.001 when compared with 1.5 cm and 3.0 cm depth dose prescriptions, respectively). Higher patient BMI resulted in a lower dose contribution of IMRT to the cord (P-values 0.066 and 0.034 when compared with 1.5 cm and 3.0 cm depth dose prescriptions respectively). CONCLUSION: IMRT of the supraclavicular fossa results in lower brachial plexus doses for patients with low BMI while patients with higher BMI benefit from lower mean cord doses. IMRT provides superior coverage of the planning target volume, especially in patients with a deeper supraclavicular fossa.