Elsevier

Medical Dosimetry

Volume 38, Issue 3, Autumn 2013, Pages 287-290
Medical Dosimetry

Implementation and evaluation of modified dynamic conformal arc (MDCA) technique for lung SBRT patients following RTOG protocols

https://doi.org/10.1016/j.meddos.2013.02.010Get rights and content

Abstract

To implement modified dynamic conformal arc (MDCA) technique and Radiation Therapy Oncology Group (RTOG) protocols in our clinic for stereotactic body radiation therapy (SBRT) treatment of patients with Stage I/II non–small cell lung cancer. Five patients with non–small cell lung cancer have been treated with SBRT. All the patients were immobilized using CIVCO Body Pro-Lok system and scanned using GE 4-slice computed tomography. The MDCA technique that was previously published was adopted as our planning technique, and RTOG protocols for the lung SBRT were followed. The patients were treated on Novalis Tx system with cone-beam computed tomography imaging guidance. All the patient plans passed the RTOG criteria. The conformal index ranges from 0.99 to 1.12 for the planning target volume, and the biological equivalent dose for the planning target volume is overall 100 Gy. Critical structures (lung, spinal cord, brachial plexus, skin, and chest wall) also meet RTOG protocols or published data. A 6-month follow-up of one of the patients shows good local disease control. We have successfully implemented the MDCA technique into our clinic for the lung SBRT program. It shows that the MDCA is useful and efficient for the lung SBRT planning, with the plan quality meeting the RTOG protocols.

Introduction

Lung cancer is the second most common cancer in both men and women. The estimated diagnosed rate was 15% of all cancers and 28% of all cancer deaths in 2007 (www.lungcancer.org). The 5-year survival rate for Stage IA is 49% and IB is 45% (www.cancer.org). Radiation therapy has been considered as one of the nonsurgical therapy methods for lung cancer treatment. With the development of more precise and accurate radiation treatment modalities, stereotactic body radiation therapy (SBRT) treatment shows high rates of local control1 with the benefit of shorter treatment time. For lung SBRT treatment, the Radiation Therapy Oncology Group (RTOG) has different clinical trials, such as 0236, 0618, 0813, and 0915 (www.rtog.org) for treatment guidelines. To develop a treatment plan so as to follow the RTOG protocols, we have to consider the treatment reproducibility, efficiency, and effectiveness. Both intensity-modulated radiation therapy (IMRT) and 3-dimensional (3D) conformal treatment can be used for lung SBRT planning depending on the protocols. Previous studies have been published on using IMRT, such as tomotherapy2 or volumetric intensity-modulated arcs3 techniques for lung SBRT planning. However, the IMRT solution is not easy to adopt mainly because the optimization algorithms are different among treatment planning systems (TPSs), and it is not easy to reproduce the same or similar optimization result. For a hospital-based organization, it is very important to have an effective and efficient way to implement a robust and transferable treatment methodology for lung SBRT planning. A recently published paper by Ross et al.4 described a modified dynamic conformal arc (MDCA) technique that can be easily implemented and transferred to other institutions. In this study, we have reported our clinical experience about implementation of the MDCA technique following RTOG protocols for 5 lung SBRT patients.

Section snippets

Patients

Three male and 2 female patients with Stage I/II lung cancer have been treated with SBRT. The age ranges from 69 to 80, and the tumor locations are distributed in either the left or right lung. The general patient information is listed in Table 1.

Simulation

All the patients were immobilized with CIVCO Body Pro-Lok system (www.civco.com) which has been proven to have accuracy and efficiency.5 A patient was positioned with both arms up and performing free breathing. Wing board and “T” cushion were used for

Results and Discussions

All the plans passed the corresponding RTOG criteria. However, in certain cases, the low-dose spillage may have minor deviation. In such a case, fine-tuning of the plan is needed. Shrinking the extended contours of the planning structures (PTV_1slc and PTV_3slc) may help to improve the low-dose spillage. Otherwise, optimization of the collimator angle for the plan may improve the plan quality. The plan summary for the PTV is listed in Table 2. Biological equivalent dose is also calculated for

Conclusions

We have reported our clinical experience by adopting the MDCA technique for lung SBRT treatment following RTOG protocols. We have successfully implemented the MDCA technique into our clinic for the lung SBRT program. It shows that the MDCA is useful and efficient for the lung SBRT planning with plan quality meeting the RTOG protocols.

References (14)

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