Dosimetric impact of mixed-energy volumetric modulated arc therapy plans for high-risk prostate cancer
Purpose: This study investigated the dosimetric impact of mixing low and high energy treatment plans for prostate cancer treated with volumetric modulated arc therapy (VMAT) technique in the form of RapidArc.
Methods: A cohort of 12 prostate cases involving proximal seminal vesicles and lymph nodes was selected for this retrospective study. For each prostate case, the single-energy plans (SEPs) and mixed-energy plans (MEPs) were generated. First, the SEPs were created using 6 mega-voltage (MV) energy for both the primary and boost plans. Second, the MEPs were created using 16 MV energy for the primary plan and 6 MV energy for the boost plan. The primary and boost MEPs used identical beam parameters and same dose optimization values as in the primary and boost SEPs for the corresponding case. The dosimetric parameters from the composite plans (SEPs and MEPs) were evaluated.
Results: The dose to the target volume was slightly higher (on average <1%) in the SEPs than in the MEPs. The conformity index (CI) and homogeneity index (HI) values between the SEPs and MEPs were comparable. The dose to rectum and bladder was always higher in the SEPs (average difference up to 3.7% for the rectum and up to 8.4% for the bladder) than in the MEPs. The mean dose to femoral heads was higher by about 0.8% (on average) in the MEPs than in the SEPs. The number of monitor units and integral dose were higher in the SEPs compared to the MEPs by average differences of 9.1% and 5.5%, respectively.
Conclusion: The preliminary results from this study suggest that use of mixed-energy VMAT plan for high-risk prostate cancer could potentially reduce the integral dose and minimize the dose to rectum and bladder, but for the higher femoral head dose.
Cite this article as:
Pokharel S. Dosimetric impact of mixed-energy volumetric modulated arc therapy plans for high-risk prostate cancer. Int J Cancer Ther Oncol 2013;1(1):01011.
NCRP. Report No, 79: Neutron contamination from medical electron accelerators. Bethesda, Maryland; NCRP: 1987.
Soderstrom S, Eklof A, Brahme A: Aspects on the optimal photon beam energy for radiation therapy. Acta Oncol 1999; 38: 179–187
Pirzkall A, Carol MP, Pickett B, Xia P, Roach M 3rd, Verhey LJ. The effect of beam energy and number of fields on photon-based IMRT for deep-seated targets. Int J Radiat Oncol Biol Phys 2002;53: 434–442.
Subramanian TS. Linear accelerators used for IMRT should be designed as small field, high intensity, intermediate energy units [For the proposition]. Med Phys 2002;29: 2526–28.
Söderstrom S, Eklöf A, Brahme A. Aspects on the optimal photon beam energy for radiation therapy. Acta Oncol 1999;38: 179–187.
Welsh JS, Mackie TR, Limmer JP. High-energy photons in IMRT: uncertainties and risks for questionable gain. Technol Cancer Res Treat 2007;6: 147–149.
Sun M and Ma L. Treatments of exceptionally large prostate cancer patients with low-energy intensity-modulated photons. J Appl Clin Med Phys 2006;7: 43–49.
Park JM, Choi CH, Ha SW, Ye SJ. The dosimetric effect of mixed-energy IMRT plans for prostate cancer. J Appl Clin Med Phys 2011;12 :3563.
Brenner DJ, Curtis RE, Hall EJ, Ron E. Second malignancies in prostate carcinoma patients after radiotherapy compared with surgery. Cancer 2000; 88: 398-406.
Hall EJ, Wuu CS. Radiation-induced second cancers: the impact of 3D-CRT and IMRT. Int J Radiat Oncol Biol Phys 2003; 56: 83-88.
Madani I, Vanderstraeten B, Bral S, et al. Comparison of 6 MV and 18 MV photons for IMRT treatment of lung cancer. Radiother Oncol 2007;82: 63–69.
Rana SB. Dose prediction accuracy of anisotropic analytical algorithm and pencil beam convolution algorithm beyond high density heterogeneity interface. South Asian J Cancer 2013; 2: 26-30.
Robinson D. Inhomogeneity correction and the analytic anisotropic algorithm. J Appl Clin Med Phys 2008; 9: 112-122.
Rana S, Rogers K. Dosimetric evaluation of Acuros XB dose calculation algorithm with measurements in predicting doses beyond different air gap thickness for smaller and larger field sizes. J Med Phys 2013;38: 9-14
Bush K, Gagne IM, Zavgorodni S, Ansbacher W, Beckham W. Dosimetric validation of Acuros XB with Monte Carlo methods for photon dose calculations. Med Phys 2011; 38: 2208-2221.
Han T, Mourtada F, Kisling K, Mikell J, Followill D, Howell R. Experimental validation of deterministic Acuros XB algorithm for IMRT and VMAT dose calculations with the Radiological Physics Center's head and neck phantom. Med Phys 2012; 39: 2193-2202.
Rana S, Rogers K, Lee T, Reed D, Biggs C. Verification and dosimetric impact of Acuros XB algorithm for stereotactic body radiation therapy (SBRT) and RapidArc planning for non-small-cell lung cancer (NSCLC) patients. Int J Med Phys Clin Eng Radiat Oncol 2013; 2: 6-14.
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