Volumetric-modulated arc therapy for oropharyngeal carcinoma: a dosimetric and delivery efficiency comparison with static-field IMRT

The effect of primary tumor volume on the prognosis of nasopharyngeal carcinoma in era of volumetric modulated arc therapy: a propensity score matched cohort study

OBJECTIVE

The role of Primary Tumor Volume (PTV) in Nasopharyngeal Carcinoma (NPC) treated with Volumetric Modulated Arc Therapy (VMAT) is still unclear. The aim of this study was to access the effect of PTV in prognosis prediction of nasopharyngeal carcinoma in era of VMAT.

METHODS

Between January 20 and November 2011, 498 consecutive NPC patients with stage I-IVA disease who received VMAT at a single center were retrospectively analyzed. Receiver Operating Characteristic (ROC) was performed to access the cut-off point of PTV. Univariate Kaplan-Meier and multivariate Cox regression analyses were used to evaluate prognostic value for PTV. The Propensity Score Matching (PSM) was used to adjust baseline potential confounders.

RESULTS

The 5-year Locol-Regional Failure-Free (L-FFR), Distant Failure-Free Survival (D-FFR), Disease-Free Survival (DFS) and Overall Survival (OS) were 90.6%, 83.7%, 71.5% and 79.3%, respectively. Before PSM, the 5-year L-FFR, D-FFR, DFS, OS rates for NPC patients with PTV ≤ 38 mL vs. PTV > 38 mL were 94.1% vs. 90.4% (p = 0.063), 87.9% vs. 76.3% (p < 0.001), 78.5% vs. 58.5% (p < 0.001) and 86.3% vs. 66.7% (p < 0.001) respectively. Multivariate analysis showed PTV was an independent prognostic factor for D-FFS (p = 0.034), DFS (p = 0.002) and OS (p = 0.001). PTV classified was still an independent prognostic factor for OS after PSM (HR = 2.034, p = 0.025.

CONCLUSIONS

PTV had a substantial impact on the prognosis of NPC patients treated with VMAT before and after PSM simultaneously. PTV > 38 mL may be considered as an indicator of the clinical stage of nasopharyngeal carcinoma.

LEVEL OF EVIDENCE

III.

Micro-CT analysis of the mandibular bone microarchitecture of rats after radiotherapy and low-power laser therapy

To investigate whether low-level laser therapy (LLLT), at different times of application (immediate and late) in the region of the parotid glands, has a distance effect on the microarchitecture of the trabecular bone in mandible of rats irradiated by volumetric modular arc therapy (VMAT). Thirty adult Wistar rats were randomly divided into placebo control groups (CG, n = 2), only radiotherapy (RG, n = 2), only LPLT (LG, n = 2), and two other groups using LLLT in the immediate time (24 h) (ILG, n = 12) and late (120 h) (LLG, n = 12) to radiotherapy by VMAT in a single dose of 12 Gy. LLLT with AsGaAl laser (660 nm, 100 mW), a spot size of 0.0028 cm², was applied in three points in the region of the right parotid gland, with energy of 2 J/cm², 20 s per point, for 10 consecutive days. After euthanasia, the right hemimandibles of each animal were dissected, prepared, and analyzed by computerized microtomography (micro-CT) and histomorphometry. The different groups were analyzed by the Tukey and Bonferroni multiple comparison tests. The micro-CT analysis found statistically significant differences between the groups, especially in the LLG, which had the highest average bone volume compared to the CG (p = 0.001) and ILG (p = 0.002) and a greater number of trabeculae than the CG (p = 0.000) and ILG (p = 0.031). The ILG also had a higher number of trabeculae than the CG (p = 0.005). Trabecula separation (Tb.Sp) was lower in the LLG (p = 0.000) and ILG (p = 0.002) when compared to the CG. In the histomorphometry, there was no statistical difference between the groups in relation to all the analyzed variables. Micro-CT analysis showed that the LLLT, even applied at a distance, both in the immediate and late VMAT times, has an effect on the mandibular bone microarchitecture by increasing the volume and number of trabeculae and decreasing the spaces between them.

Prognostic Relevance of Change in Body Mass Index in Patients With Nasopharyngeal Carcinoma Undergoing Volumetric Modulated Arc Therapy: A Retrospective Study

Objective

To assess the effect of pretreatment body mass index (BMI) and the extent of change in BMI (ΔBMI) during the treatment course on the treatment outcomes in patients with nasopharyngeal carcinoma (NPC) receiving volumetric modulated arc therapy (VMAT).

Methods

Data pertaining to 498 consecutive NPC patients with stage I–IVA disease who received VMAT between January 2010 and November 2011 at a single center were retrospectively analyzed. Univariate Kaplan-Meier and multivariate Cox regression analyses were used to evaluate the prognostic significance of pretreatment BMI and ΔBMI. Receiver operating characteristic (ROC) curve analysis was used to determine the optimal cut-off point of ΔBMI.

Results

The 5-year loco-regional failure-free (L-FFR), distant failure-free survival (D-FFR), disease-free survival (DFS), and overall survival (OS) rates were 90.6%, 83.7%, 71.5% and 79.3%, respectively. The 5-year L-FFR, D-FFR, DFS, OS rates for NPC patients with ΔBMI ≤1 kg/m² vs ΔBMI >1 kg/m² were 92.3% vs 89.3% (P = .137), 90.9% vs 78.5% (P < .001), 80.4% vs 65.1% (P < .001), and 88.0% vs 73.0% (P < .001), respectively. ΔBMI >1 kg/m² was an independent predictor of D-FFR (P = .002), DFS (P = .002), and OS (P = .001).

Conclusions

ΔBMI during treatment course may have a significant impact on the prognosis of NPC patients receiving VMAT.

Clinical performance of FractionLab in patient-specific quality assurance for intensity-modulated radiotherapy

Background

This study was aimed at comparing and analyzing the results of FractionLab (Varian/Mobius Medical System) with those of portal dosimetry that uses an electronic portal imaging device. Portal dosimetry is extensively used for patient-specific quality assurance (QA) in intensity-modulated radiotherapy (IMRT).

Methods

The study includes 29 patients who underwent IMRT on a Novalis-Tx linear accelerator (Varian Medical System and BrainLAB) between June 2019 and March 2021. We analyzed the multileaf collimator DynaLog files generated after portal dosimetry to evaluate the same condition using FractionLab. The results of the recently launched FractionLab at various gamma indices (0.1%/0.1 mm–1%/1 mm) are analyzed and compared with those of portal dosimetry (3%/3 mm).

Results

The average gamma passing rates of portal dosimetry (3%/3 mm) and FractionLab are 98.1% (95.5%–100%) and 97.5% (92.3%–99.7%) at 0.6%/0.6 mm, respectively. The results of portal dosimetry (3%/3 mm) are statistically comparable with the QA results of FractionLab (0.6%/0.6 mm–0.9%/0.9 mm).

Conclusion

This paper presents the clinical performance of FractionLab by the comparison of the QA results of FractionLab using portal dosimetry with various gamma indexes when performing patient-specific QA in IMRT treatment. Further, the appropriate gamma index when performing patient-specific QA with FractionLab is provided.

Machine Learning to Predict Treatment in Oropharyngeal Squamous Cell Carcinoma

OBJECTIVES

This study seeks to (1) demonstrate how machine learning (ML) can be used for prediction modeling by predicting the treatment patients with T1-2, N0-N1 oropharyngeal squamous cell carcinoma (OPSCC) receive and (2) assess the impact patient, socioeconomic, regional, and institutional factors have in the treatment of this population.

METHODS

A retrospective cohort of adults diagnosed with T1-2, N0-N1 OPSCC from 2004 to 2013 was obtained using the National Cancer Database. The data was split into 80/20 distribution for training and testing, respectively. Various ML algorithms were explored for development. Area under the curve (AUC), accuracy, precision, and recall were calculated for the final model.

RESULTS

Among the 19,111 patients in the study, the mean (standard deviation) age was 61.3 (10.8) years, 14,034 (73%) were male, and 17,292 (91%) were white. Surgery was the primary treatment in 9,533 (50%) cases and radiation in 9,578 (50%) cases. The model heavily utilized T-stage, primary site, N-stage, grade, and type of treatment facility to predict the primary treatment modality. The final model yielded an AUC of 78% (95% CI, 77-79%), accuracy of 71%, precision of 72%, and recall of 71%.

CONCLUSION

This study created a ML model utilizing clinical variables to predict primary treatment modality for T1-2, N0-N1 OPSCC. This study demonstrates how ML can be used for prediction modeling while also highlighting that tumor and facility realted variables impact the decision making process on a national level.

Correlation between plan quality improvements and reduced acute dysphagia and xerostomia in the definitive treatment of oropharyngeal squamous cell carcinoma

BACKGROUND

To evaluate plan quality using volumetric-modulated arc therapy (VMAT) and step-and-shoot intensity-modulated radiation therapy (SS-IMRT) techniques and for patients treated for oropharyngeal squamous cell carcinoma (OPSCC).

METHODS

Treatment plans for patients treated definitively for stages I-IVb, OPSCC between December 2009 and August 2015 were retrospectively reviewed. Dosimetric endpoints of involved organs-at-risk (OARs) were retrieved from clinical plans. Common Terminology Criteria for Adverse Events scores of acute toxicities were compared.

RESULTS

Two-hundred twenty-two patients were identified with 134 and 88 receiving SS-IMRT and VMAT with median follow-up time of 23.0 and 7.9 months, respectively. The dosimetric endpoints of the OARs were significantly improved in VMAT cohort, which translated into significantly lower rates of grade 2 or higher acute dysphagia and xerostomia.

CONCLUSION

Improvements in stages I-IVb, oropharyngeal cancer plan quality are associated with reduced grade ≥ 2 acute dysphagia and xerostomia.

[Comparison of planning quality and delivery efficiency between volumetric modulated arc therapy and dynamic intensity modulated radiation therapy for nasopharyngeal carcinoma with more than 4 prescribed dose levels]

The aim of this study is to compare the planning quality and delivery efficiency between dynamic intensity modulated radiation therapy (d-IMRT) and dual arc volumetric modulated arc therapy (VMAT) systematically for nasopharyngeal carcinoma (NPC) patients with multi-prescribed dose levels, and to analyze the correlations between target volumes and plan qualities. A total of 20 patients of NPC with 4-5 prescribed dose levels to achieve simultaneous integrated boost (SIB) treated by sliding window d-IMRT in our department from 2014 to 2015 were re-planned with dual arc VMAT. All optimization objectives for each VMAT plan were as the same as the corresponding d-IMRT plan. The dose parameters for targets and organ at risk (OAR), the delivery time and monitor units (MU) in two sets of plans were compared respectively. The treatment accuracy was tested by three dimensional dose validation system. Finally, the correlations between the difference of planning quality and the volume of targets were discussed. The conform indexes (CIs) of planning target volumes (PTVs) in VMAT plans were obviously high than those in d-IMRT plans ( P < 0.05), but no significant correlations between the difference of CIs and the volume of targets were discovered ( P > 0.05). The target coverage and heterogeneity indexes (HIs) of PTV 1 and PGTV nd and PTV 3 in two sets of plans were consistent. The doses of PTV 2 decreased and HIs were worse in VMAT plans. VMAT could provide better spinal cord and brainstem sparing, but increase mean dose of parotids. The average number of MUs and delivery time for d-IMRT were 3.32 and 2.19 times of that for VMAT. The γ-index (3 mm, 3%) analysis for each plans was more than 97% in COMPASS ® measurement for quality assurance (QA). The results show that target dose coverages in d-IMRT and VMAT plans are similar for NPC with multi-prescribed dose levels. VMAT could improve the the CIs of targets, but reduce the dose to the target volume in neck except for PGTV nd. The biggest advantages of VMAT over d-IMRT are delivery efficiency and QA.

Clinical outcomes of concurrent chemoradiotherapy with volumetric modulated arc therapy in patients with locally advanced nasopharyngeal carcinoma

PURPOSE

The purpose of this study was to analyze the clinical results of concurrent chemoradiotherapy (CCRT) with volumetric modulated arc therapy (VMAT) for nasopharyngeal carcinoma (NPC) patients.

MATERIALS AND METHODS

Patients with stage II-IVB NPC who received CCRT with VMAT between 2010 and 2014 were included in this study. The planned dose was 70 Gy in 35 fractions.

RESULTS

Twenty patients aged between 28 and 85 years (median 60 years) were assessed. With a median follow-up time of 47 months, the 3-year overall survival and progression-free survival rates were 85 and 65%, respectively. The 3-year local, regional and distant control rates were 78, 88 and 79%, respectively. At 0, 3, 6 and 12 months from CCRT, 19, 6, 3, and 1 patients had grade 2 dry mouth, respectively. No cases of grade 3 or worse dry mouth were observed. The severity of dry mouth was downgraded from grade 2 to grade 0 or 1 significantly earlier in younger patients (<70 years, p = 0.02) or patients in whom the mean dose to one parotid gland was lower (<26 Gy, p = 0.04).

CONCLUSIONS

Our clinical results regarding CCRT with VMAT for NPC patients showed favorable survival rates while maintaining organ function.

Automated IMRT planning in Pinnacle : A study in head-and-neck cancer

PURPOSE

This study evaluates the performance and planning efficacy of the Auto-Planning (AP) module in the clinical version of Pinnacle 9.10 (Philips Radiation Oncology Systems, Fitchburg, WI, USA).

METHODS AND MATERIALS

Twenty automated intensity-modulated radiotherapy (IMRT) plans were compared with the original manually planned clinical IMRT plans from patients with oropharyngeal cancer.

RESULTS

Auto-Planning with IMRT offers similar coverage of the planning target volume as the original manually planned clinical plans, as well as better sparing of the contralateral parotid gland, contralateral submandibular gland, larynx, mandible, and brainstem. The mean dose of the contralateral parotid gland and contralateral submandibular gland could be reduced by 2.5 Gy and 1.7 Gy on average. The number of monitor units was reduced with an average of 143.9 (18%). Hands-on planning time was reduced from 1.5-3 h to less than 1 h.

CONCLUSIONS

The Auto-Planning module was able to produce clinically acceptable head and neck IMRT plans with consistent quality.

Plan quality and delivery time comparisons between volumetric modulated arc therapy and intensity modulated radiation therapy for scalp angiosarcoma: A planning study

Introduction

Due to its spherical surface, scalp angiosarcoma requires careful consideration for radiation therapy planning and dose delivery. Herein, we investigated whether volumetric modulated arc therapy (VMAT) is superior to intensity modulated radiation therapy (IMRT) in terms of the plan quality and delivery time.

Methods

Three different coplanar treatment plans were created for four patients, comprising a two‐arc VMAT plan as well as 5‐field and 9‐field IMRT plans with 6 MV beams. The X‐ray Voxel Monte Carlo algorithm was employed for dose calculation. A radiation therapy dose of 60 Gy was prescribed to the planning target volume (PTV) in 30 fractions. The homogeneity indexes (HIs) and conformity indexes (CIs) of the PTV, organs at risk (OARs) doses and delivery times were calculated and compared.

Results

For the VMAT, 5‐field and 9‐field IMRT plans, the mean HIs were 0.14, 0.16 and 0.15; CIs_100% were 0.63, 0.61 and 0.64; CIs_98% were 0.72, 0.66 and 0.70 and CIs_95% were 0.74, 0.67 and 0.71 respectively. All mean dose parameters of the VMAT and 9‐field IMRT plans for the brain were equal to or lower than those of the 5‐field IMRT plan. For the 5‐field IMRT plan, the dose constraints for the left lens were not satisfied in two patients. The mean delivery times were 3.3, 11.1 and 14.7 min for the VMAT, 5‐field and 9‐field IMRT plans respectively.

Conclusion

The VMAT plan quality is comparable to that of 9‐field IMRT, with a reduced delivery time. Therefore, VMAT represents a valuable, sophisticated irradiation technique for treating scalp angiosarcoma.