Comparison between two treatment planning systems for volumetric modulated arc therapy optimization for prostate cancer

doi:10.1016/j.ejmp.2012.10.003

Physica Medica

Volume 30, Issue 1, February 2014, Pages 2-9

https://doi.org/10.1016/j.ejmp.2012.10.003 Get rights and content

Abstract

Purpose

To investigate the performances of two commercial treatment planning systems (TPS) for Volumetric Modulated Arc Therapy (VMAT) optimization regarding prostate cancer. The TPS were compared in terms of dose distributions, treatment delivery parameters and quality control results.

Materials and methods

For ten patients, two VMAT plans were generated: one with Monaco TPS (Elekta) and one with Pinnacle TPS (Philips Medical Systems). The total prescribed dose was 78 Gy delivered in one 360° arc with a Synergy^® linear accelerator equipped with a MLCi2^®.

Results

VMAT with Monaco provided better homogeneity and conformity indexes but lower mean dose to PTVs than Pinnacle. For the bladder wall (p = 0.019), the femoral heads (p = 0.017), and healthy tissues (p = 0.005), significantly lower mean doses were found using Monaco. For the rectal wall, VMAT with Pinnacle provided a significantly (p = 0.047) lower mean dose, and lower dose into 50% of the volume (p = 0.047) compared to Monaco. Despite a greater number of monitor units (factor 1.5) for Monaco TPS, the total treatment time was equivalent to that of Pinnacle. The treatment delivery parameter analysis showed larger mean MLC area for Pinnacle and lower mean dose rate compared to Monaco. The quality control results gave a high passing rate (>97.4%) for the gamma index for both TPS but Monaco provided slightly better results.

Conclusion

For prostate cancer patients, VMAT treatment plans obtained with Monaco and Pinnacle offered clinically acceptable dose distributions. Further investigations are in progress to confirm the performances of the two TPS for irradiating more complex volumes.

Introduction

Volumetric modulated arc therapy (VMAT) is a new radiotherapy technique which allows to achieve treatment plans of similar or improved quality compared to fixed-field intensity-modulated radiation therapy (IMRT) while reducing the treatment time per fraction [1]. In practice, to obtain highly modulated dose distributions delivered efficiently, a treatment planning system (TPS) with a powerful optimization and segmentation algorithm is required.

While a lot of users are in the process of replacing fixed-field IMRT by VMAT, or directly implementing VMAT in their radiotherapy department, there is a lack of information concerning the relative performances of the mainly used TPS for VMAT planning. To our knowledge, only three studies deal with this topic [2], [3], [4]. In Rao et al., ERGO++ (Elekta, Crawley, UK) was compared to Pinnacle (Philips Medical Systems, Madison, WI) direct machine parameter optimization (DMPO) combined with a home-made arc-sequencer and Pinnacle SmartArc inverse planning module [2]. In Masi et al., the performances of Monaco (CMS-Elekta, Crawley, UK) were compared to ERGO++ and Oncentra (Nucletron-Elekta) [3]. Finally, in Wiezorek et al., VMAT plans obtained with Monaco and Eclipse (Varian Medical System, Palo Alto, CA) were evaluated [4]. In these studies, the comparisons were made by fixing common planning objectives on PTVs and OARs and comparing the dosimetric results and treatment delivery efficiency (number of monitor units and treatment time).

The aim of the present study was to investigate the performances of two TPS that have not been compared yet in VMAT mode, both using different approaches for VMAT plan optimization: Monaco based on a two-stage constrained optimization [5] and Pinnacle SmartArc [6]. This work was performed by two institutions. The aim was to compare VMAT plans performed by Monaco and Pinnacle regarding to dosimetric performances and treatment delivery specificities. We therefore fully put in evidence the differences observed in terms of dose distributions, delivery efficiency, treatment delivery parameters (mean dose rate, mean segment area) and quality control results on 10 prostate cancer cases.

Section snippets

Patients

Ten prostate adenocarcinoma patients referred to our institutions for a radical external beam irradiation to the prostate and seminal vesicles (SV) were considered for this dosimetric comparative analysis.

Anatomic data acquisition, volumes definition and dose

Organs at risk [rectal wall (5 mm thickness), bladder wall (7 mm thickness), femoral heads (FH)] and target volumes (prostate, SV) were delineated on dedicated 2 mm-thick CT slices.

The first clinical target volume (CTV1) comprised the prostate and SV. The CTV2 was limited to the prostate only.

Dose distribution

The patient-averaged differences in the dose distributions for the two TPS are shown in Fig. 1. Large differences are observed. First, Monaco favored the dose delivery on gantry angles that allowed crossing a minimum volume of healthy tissue to reach the PTV. Therefore, the volume of healthy tissue receiving higher doses was more important with Pinnacle than with Monaco. Furthermore, we observed that Pinnacle solutions result in more dose delivered on the left–right direction (i.e. around the

Discussion

The aim of the present study was to investigate the performances of Monaco and Pinnacle TPS for VMAT plan optimization. To our knowledge, this is the first study yielding a global comparison of two TPS for VMAT planning, from the prescription phase and dose distribution evaluation to the delivery efficiency. We also included beam geometry, treatment delivery parameters and quality control results.

For prostate cancer, VMAT solutions proposed by both TPS offered good PTV coverage and OARs

Conclusion

For prostate cancer patients, VMAT planned with Monaco and Pinnacle TPS offered clinically acceptable dose distributions. Monaco plans showed enhanced OAR sparing but lower doses into the PTV compared to Pinnacle plans. Similar delivery times were found for both TPS but Pinnacle solution required less MUs. Finally, a good dosimetric agreement with measured doses was achieved with both TPS, but Monaco offered a slightly higher passing rate in the gamma index analysis. Further investigations are

Conflicts of interest

Caroline Lafond' contribution is part of a PhD thesis supported by a grant from Elekta.

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Ten patients with breast cancer were considered. Dose prescriptions were: 48 Gy and 40.5 Gy in 15 fractions to, respectively, PTV_Boost and PTV_WholeBreast. A reference plan was optimized and four more plans using the “MU Objective”, a tool for total MU controlling, were prepared imposing ±20 and ±50% total MU for inducing different complexities. Plan objectives were: D_95% > 95% for both PTVs, and D_2% < 107% for PTV_Boost; mean dose < 9.5 Gy and V_{20 Gy} < 10% for ipsilateral lung; V_{18 Gy} < 5% for heart; mean dose <3 Gy for controlateral breast; furthermore V_{5 Gy}, V_{10 Gy} , V_{20 Gy}, and V_{30 Gy} to body were minimized. Plans were evaluated in terms of technical parameters, dosimetric plan objectives findings and pre-treatment quality assurance (QA).
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Review paperComparison between two treatment planning systems for volumetric modulated arc therapy optimization for prostate cancer

Abstract

Purpose

Materials and methods

Results

Conclusion

Introduction

Section snippets

Patients

Anatomic data acquisition, volumes definition and dose

Dose distribution

Discussion

Conclusion

Conflicts of interest

Int J Radiat Oncol Biol Phys

Int J Radiat Oncol Biol Phys

Med Image Anal

Radiother Oncol

Int J Radiat Oncol Biol Phys

Int J Radiat Oncol Biol Phys

Int J Radiat Oncol Biol Phys

Volumetric modulated arc therapy: IMRT in a single gantry arc

Med Phys

Comparison of Elekta VMAT with helical tomotherapy and fixed field IMRT: plan quality, delivery efficiency and accuracy

Med Phys

Rotational IMRT techniques compared to fixed gantry IMRT and tomotherapy: multi-institutional planning study for head-and-neck cases

Radiat Oncol

Review paper
Comparison between two treatment planning systems for volumetric modulated arc therapy optimization for prostate cancer