Draft Key Questions
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Archived: This report is greater than 3 years old. Findings may be used for research purposes, but should not be considered current.
Conduct a systematic literature scan for published data for the treatment of stereotactic body radiation therapy (SBRT) and provide a broad overview of the current state of SBRT for solid malignant tumors.
Ovid, MEDLINE, EMBASE, the Cochrane Database, and the Health Technology Assessment Database from January 2000 to December 2010. We also searched www.ClinicalTrials.gov, www.fda.gov, and gray literature within Windhover, Current HC News, Gray Sheet, The Wall Street Journal, Clinica, and the Google search engine.
Clinical studies of any design, published in English that delivered SBRT in 10 or fewer fractions, and enrolled at least three patients with solid malignant tumors in the body (excluding head and spine) were included. Two reviewers abstracted information on study design, patients, and reported outcomes. We synthesized the following variables if reported: cancer type, patient inclusion criteria, type of radiation, instrumentation, and algorithms used, study design and size, comparators, concurrent and/or prior treatments, length of followup, outcomes measured, and adverse events.
Our searches identified a total of 124 relevant prospective and retrospective single group studies. The bulk of the studies examined SBRT for tumors of the lung/thorax (k = 68). We found 27 studies of tumors located in the pancreas, liver, colon, and fewer than 10 studies each for sites within uterus, pelvis, sacrum, kidney, prostate, and thyroid. There were 10 studies that included multiple treatment sites within the study. Study designs for SBRT include prospective and retrospective single group studies. Study size varied from 3 (minimum acceptable for inclusion in this review) to 398 patients. None of the published trials were comparative studies. Reported patient inclusion criteria include inoperable tumors, patients refusing surgery, biopsy proven disease, life expectancy, no prior radiation therapy (RT) or prior RT received in a particular time frame prior to SBRT, and required performance levels on the Karnofsky or World Health Organization/Eastern Cooperative Oncology Group scales. Several studies reported the use of modified linacs(k = 47), CyberKnife (k = 39), Novalis Shaped Beam or Clinac (k = 16), Body GammaKnife (k=1), Tomotherapy Hi-Art(k = 2), FOCAL unit(k = 1), and Synergy systems(k = 6). Typically, inverse treatment planning algorithms; pencil beam algorithms for dose calculation; and tissue maximum ratio calculation algorithms were reported. Prior treatments reported include surgery, radiation therapy (e.g., intensity-modulated radiation therapy (IMRT), brachytherapy), pharmaceuticals (e.g., tamoxifen), and/or chemotherapy. We calculated an overall mean and median for the length of followup for each cancer type. The shortest mean and median followup was within the multiple site category (12.9 and 8.2 months [1–95 months] respectively). Studies of the tumors involving the pelvis, sacrum, and uterus had the longest mean/median followup (31 and 33 months [range 2–77 months]). The reported outcomes include tumor control/response, toxicity, and overall survival. Most studies used four criteria to measure tumor control/tumor response: complete response, partial response, stable disease, and progression of disease. The most frequently reported adverse events include pain, fatigue, nausea, bleeding, and diarrhea.
In brief, SBRT appears to be widely disseminated for treatment of a variety of cancer types, although a majority of studies have only focused on treatment of thoracic tumors. None of the currently available studies include comparison groups. Comparative studies are needed to provide evidence that the theoretical advantages of SBRT over other radiotherapies actually occur in the clinical setting. Currently, there is only one small ongoing trial doing so. Consequently, a full systematic review of the current literature cannot answer questions on the effectiveness and safety of SBRT compared to other radiotherapy interventions.