Journal of the National Cancer Institute Advance Access published online on February 26, 2008
JNCI Journal of the National Cancer Institute, doi:10.1093/jnci/djn020
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Intensity-Modulated Radiation Therapy Dose Prescription, Recording, and Delivery: Patterns of Variability Among Institutions and Treatment Planning Systems
Affiliations of authors: Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA (IJD, EG); Department of Radiation Oncology, Morristown Memorial Hospital, Morristown, NJ (CWC); Department of Radiation Oncology, Kennedy Health System, Sewell, NJ (KLC); Department of Radiation Oncology, Ochsner Clinic Foundation, New Orleans, LA (RKM); Department of Radiation Oncology, Reid Hospital & Health Care Service, Richmond, IN (SPS)
Correspondence to: Indra J. Das, FACR, Department of Radiation Oncology, University of Pennsylvania, 2 Donner Bldg, 3400 Spruce St, Philadelphia, PA 19104 (e-mail: das{at}xrt.upenn.edu).
Background: Intensity-modulated radiation therapy (IMRT) is a widely accepted method for radiation treatment to provide a prescribed and uniform dose to the target volume and a minimum dose to normal tissues that is dependent on the IMRT software and the treatment machine. We examined the variation in IMRT dose prescription, treatment planning, dose recording, and dose delivery among cancer patients who were treated with different treatment planning systems at different medical institutions to assess variability in patient care.
Methods: We conducted a retrospective analysis of 803 patients who were treated with IMRT between October 2004 and July 2006 for brain, head and neck, or prostate cancer at five medical institutions that used different treatment planning systems. The prescribed dose to the target volume, as recorded in the chart or as noted in the electronic data management system, was extracted for each patient. The planned dose that was delivered to the patient, as represented in the dose–volume histogram, was acquired from each treatment planning system. The actual minimum, maximum, median, and isocenter doses to the target volume were normalized to the prescribed dose and analyzed for each disease site and institution.
Results: Of the 803 patients, 12% were treated for brain cancer, 26% for head and neck cancer, and 62% for prostate cancer. The recorded dose variability from prescription was widespread for the minimum, maximum, and isocenter doses. A total of 46% of the patients received a maximum dose that was more than 10% higher than the prescribed dose, and 63% of the patients received a dose that was more than 10% lower than the prescribed dose. At all five institutions, the prostate cancer cases had the smallest dosimetric variation and the head and neck cancer cases had the largest variation. The median dose to the target varied from the prescribed dose by ±2% in 68% of the patients, by ±5% in 88% of the patients, and by ±10% in 96% of the patients. The recorded isocenter dose varied from prescription for all disease sites and treatment planning systems.
Conclusions: Substantial variation in the prescribed and delivered doses exists among medical institutions, raising concerns about the validity of comparing clinical outcomes for IMRT. The isocenter dose in IMRT is simply a point dose and often does not reflect the prescription dose that is specified by a selected isodose line encompassing the target volume. This study suggests the need for national and/or international guidelines for dose prescription, planning, and reporting for a meaningful clinical trial in IMRT.
| CONTEXT AND CAVEATS Prior knowledge Intensity-modulated radiation therapy (IMRT) is widely used to treat cancer because it provides a prescribed and uniform radiation dose to the target while minimizing the radiation dose to normal tissues. In IMRT, many factors, including special software, are required to plan treatments and control the radiation dose during therapy. Variations in these factors can affect the dose and, consequently, the clinical outcome. Study design A retrospective analysis of treatment parameters for 803 patients who were treated with IMRT for brain, head and neck, or prostate cancer at five medical institutions that used different treatment planning systems. Contribution In IMRT, the prescribed dose rarely corresponded to the planned, or delivered, dose. At all five institutions, dosimetric variation was smallest for the prostate cancer cases and largest for the head and neck cancer cases. The recorded delivered dose varied from the prescribed dose for all disease sites and treatment planning systems. Implications The substantial variation in the prescribed and delivered doses that exists among medical institutions raises concerns about the validity of comparing clinical outcomes for IMRT. National and/or international guidelines for dose prescription, planning, and reporting in IMRT are needed. Limitations The medical institutions differed with respect to volume delineation, the availability of quality-assurance data for the treatment planning algorithms, and the uniformity of IMRT input constraints. Only five treatment planning systems from five institutions, some of which had limited IMRT planning data in certain disease sites, were included.
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Manuscript received August 29, 2007; revised December 20, 2007; accepted January 14, 2008.
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J Natl Cancer Inst 2008 100: 1263.
J Natl Cancer Inst 2008 100: 1263-1264.
J Natl Cancer Inst 2008 100: 1264.
J Natl Cancer Inst 2008 100: 1264-1265.
J Natl Cancer Inst 2008 100: 288-290.
J Natl Cancer Inst 2008 100: 287.
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