CHICAGO, Nov. 10 Clinicians using RapidArc® radiotherapy technology for fast, precise, non-invasive cancer treatments have found that they are able to substantially reduce scatter dose to surrounding healthy tissues, according to several presentations and posters presented this week at the annual meeting of the American Society for Radiation Oncology (ASTRO) in Chicago. With RapidArc, doctors were able to quickly administer image-guided radiotherapy or radiosurgery treatments using fewer monitor units, which translates to less total body irradiation during treatment. In addition, a number of planning studies documented the clinical advantages of RapidArc over other forms of intensity-modulated radiotherapy (IMRT).
ASTRO is the largest association of radiation oncology professionals in the world, with 10,000 members, including radiation oncologists, radiation oncology nurses, medical physicists, radiation therapists, dosimetrists and biologists. The 2009 meeting was held in Chicago, Illinois, from November 1-5. Some of the highlights:
In the vast majority of cases, RapidArc treatments for prostate cancer result in equal or better tumor coverage with less dose to the bladder and rectum, compared to conventional fixed-field IMRT, according to a research team from the Finsen Centre(*) in Copenhagen, Denmark. The RapidArc treatments also use much fewer monitor units--a two to three-fold decrease--which means that less scattered, non-therapeutic radiation is delivered during these treatments, which took, on average, 1.25 minutes to deliver once patients were positioned for treatment.(1)
These results were echoed by researchers at the University of Alabama, Birmingham (UAB(*)), who found that RapidArc is more efficient in terms of delivery time and the number of monitor units needed, and produces treatment plans "that meet both target coverage and normal tissue constraints for all three prostate risk categories."(2)
In comparing RapidArc with helical tomotherapy for the treatment of pancreatic cancer, a team of researchers from the University of Virginia found that the two approaches can generate comparable IMRT treatment plans; however, RapidArc may have a dosimetric advantage due to faster treatments using fewer monitor units.(3) A group from the VU University Medical Center in Amsterdam (VUMC(*)) reported that, for pancreatic cancer, the conformity index (a measure of plan quality) was higher for RapidArc plans than for conventional IMRT plans, with better sparing of surrounding organs. "The speed of planning and delivery favors RapidArc over five-field IMRT, particularly as the risk of intra-fractional motion is correlated with treatment duration," they concluded.(4)
A team from the Brown Cancer Center at the University of Louisville reported that a two-arc RapidArc plan offers the same level of dose homogeneity and tissue sparing as fixed-field IMRT. The RapidArc treatments, however, are faster to deliver, even with two arcs. "The reduction in treatment time is a benefit to image-guided radiation therapy (IGRT) and consequently to SBRT," the researchers assert.(5) Another team from the University of Virginia found that the treatment of peripheral lung lesions using RapidArc is dosimetrically equivalent to fixed-gantry IMRT, however, "low dose spillage trended toward improvement, which may reduce the incidence of symptomatic radiation-induced pneumonitis."
Emory University researchers compared RapidArc with non-rotational IMRT in the treatment of pediatric brain tumors. The team observed that tumor coverage is comparable between the two approaches, however, RapidArc reduces treatment duration and the amount of dose going to normal tissues throughout the body. "Pediatric patients would benefit from shortened treatment times, potentially reducing the use of anesthesia," they concluded, adding that the decreased total body irradiation could also potentially reduce the number of late effects, including the risk of secondary malignancies later in life.(6)
A team from the Centre Regional de Lutte Contre le Cancer Val d'Aurelle in Montpellier, France, compared RapidArc to IMRT for the treatment of anal canal cancer, finding that RapidArc with two arcs delivered equivalent treatment plans in terms of target coverage and sparing of organs at risk. RapidArc "provided significant reductions in MU and treatment time per fraction," they stated. "These improvements should reduce patient discomfort, allow more quality control, and may increase treatment acceptance compared to IMRT."(7)
Abstracts for these and other presentations and posters presented at this year's ASTRO meeting are available at the ASTRO website and also, in the "Proceedings of the American Society for Radiation Oncology 51st Annual Meeting," International Journal of Radiation Oncology, Biology, Physics, Volume 75, Issue 3, Supplement .
(*)One or more members of this research team received research grant support from Varian Medical Systems.
(1) S. A. Engelholm, S. S. Korreman, P. M. Petersen, M. Aznar, F. Kjaer-Kristoffersen. Intensity Modulated Single Arc Therapy (RapidArc(TM)) of Prostate Cancer.
(2) R. Popple, J. B. Fiveash, M. C. Dobelbower, R. Jacob, R. Y. Kim, I. A. Brezovich. Prostate Treatment Using Intensity Modulated Arc Therapy: Clinical Experience and Comparison with DMLC IMRT.
(3) J. Cai, R. McLawhorn, W. Yang, K. Wijesooriya, N. Dunlap, C. Geesey, K. Sheng, T. Rich, S. Benedict. Dosimetric Comparison Of 6 MV And 15 MV RapidArc To Helical Tomotherapy For The Treatment Of Pancreatic Cancer.
(4) W. Eppinga, F. J. Lagerwaard, W. F. A. R. Verbakel, B. J. Slotman, S. Senan, Conventional IMRT Versus Volumetric Modulated Arc Therapy (RapidArc) For Pancreatic Cancer .
(5) A. D. Zacarias, M. Brown, M. Mills . Comparison of Eclipse Fixed Field IMRT and RapidArc VMAT for Stereotactic Body Radiotherapy of the Lung.
(6) D. O. Ansari, N. Esiashvili, A. H. Dhabaan, C. S. Jarrio, E. S. Elder, M. Crowder, W. Koontz-Raisig, H. G. Shu. Is Intensity Modulated Arc Therapy (IMAT) Better Than Non-rotational Intensity Modulated Radiation Therapy (IMRT) For Pediatric Brain Tumors?
(7) J. Dubois, S. Vieillot, C. Llacer Moscardo, C. Lemanski, D. Azria, P. Fenoglietto. A Planning Study To Compare Plans Using Volumetric Modulated Arc Therapy Or Intensity-modulated Radiation Therapy For The Treatment Of Anal Canal Cancer.
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