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Tipton KN, Sullivan N, Bruening W, et al. Stereotactic Body Radiation Therapy [Internet]. Rockville (MD): Agency for Healthcare Research and Quality (US); 2011 May. (Comparative Effectiveness Technical Briefs, No. 6.)

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Stereotactic Body Radiation Therapy [Internet].

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Discussion

This Technical Brief provides a broad overview of the current state of SBRT. Aspects of the brief include current technologies available to deliver SBRT; types and locations of tumors that have been treated with SBRT; the possible advantages and disadvantages of the technology; the extent of diffusion of the technology; and information about advances in the technology that are currently in development. We searched the Internet for gray literature to identify information for cancer sites, theoretical advantages and disadvantages of SBRT, and potential safety issues and harms. Specialized instrumentation for SBRT, the FDA status, technologies in development, and an estimate of the number of hospitals performing SBRT in the United States were also explored using the Internet. The information collected for Guiding Questions 1 and 2 may not be inclusive of all resources. For Guiding Question 3, we performed a systematic search of bibliographic databases, including MEDLINE, EMBASE, and Cochrane. If the literature searches for Guiding Question 3 returned relevant information, we also included it in the first two Guiding Questions. We also searched ClinicalTrials.gov to determine if any trials are currently in progress for SBRT. Appendix K lists the condition being studied, the intervention, study design, primary and secondary outcomes to be measured, estimated enrollment, planned duration, and location of ongoing trials.

The available literature addressing SBRT is considerably large. The bulk of the studies were for tumors located in the lung/thorax (k = 68). We found fewer than 10 studies each for tumors of the pancreas, liver, colon, uterus, pelvis, sacrum, kidney, prostate, and thyroid. This literature base also includes many theoretical treatment-planning studies and treatment technique studies. The study designs identified in our literature search for SBRT treatment included prospective and retrospective single-group studies. There were several studies that included duplicate populations.

Our literature search did not identify any published comparison (whether randomized or nonrandomized) studies. Currently (as of September 2010), there is one ongoing nonrandomized trial comparing two methods of delivering SBRT to conformal radiation for management of NSCLC with a planned enrollment of 120 patients. There are also two ongoing randomized clinical trials comparing SBRT vs. primary resection for lung cancer (see Appendix K, Ongoing Clinical Trials). A third randomized trial is comparing SBRT delivered in one vs. three fractions for NSCLC.

External beam radiation treatment has long been a mainstay of cancer treatment. Advances in this technology have allowed smaller and hard-to-target tumors to be treated; reducing the amount of radiation received by adjacent healthy tissue. SBRT requires accuracy in delivery of the high dose of radiation, patient immobilization, target localization, maneuvers to either limit or compensate for target movement (tracking software), and the use of stereotaxy. It can be completed in one to five fractions and may be a treatment option for patients who refuse surgery, for tumors considered inoperable, or when traditional RT is not an option.

One of the most critical aspects of SBRT is ensuring accurate delivery of the intended dose to the intended target, particularly given the higher dose of radiation typically used. This requires rigorous quality control and quality assurance measures for treatment planning and treatment delivery. Tumor sites within the body tend to move (e.g., respiratory movement) between fractionated treatments, causing difficulties immobilizing the targeted tumor. Therefore, tumor tracking techniques will continue to play an integral role in the procedure. Considerations for selection of appropriate treatment candidates include prior radiation history of the treatment tissues, treatment volume, organ function, capacity for recovery, number of sites of disease, and many other individual cancer-related factors.9

Groups such as the American Association of Physicists in Medicine (AAPM) have urged participation in trials sponsored by the National Cancer Institute (NCI), or in trials run by the NCI-sponsored Radiation Therapy Oncology Group, a multi-institutional research cooperative. In a recent guidance document, AAPM pointed out that protocol-driven treatment in the context of such studies would reflect the guidelines produced by experts in the field (Also available: http://www.aapm.org/pubs/reports/RPT_101.pdf.).158 Future studies may help to determine the optimal number of radiation fractions, the minimum and maximum dose per fraction, the maximum number and diameter of lesions for various locations, and the radiobiological explanations for the efficacy of SBRT treatment.

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