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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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Executive Summary

Background

The development of stereotactic body radiation therapy (SBRT) began in the early 1990s at the Karolinska Institute (Stockholm, Sweden) with researchers Ingmar Lax and Henric Blomgren and was derived from the techniques and procedures of stereotactic radiosurgery (SRS). Researchers in Japan and North America helped develop this treatment during this same time in the 1990s. The American College of Radiology (ACR) and the American Society for Radiation Oncology (ASTRO) define SBRT as “an external beam radiation therapy method used to very precisely deliver a high dose of radiation to an extracranial target within the body, using either a single dose or a small number of fractions.”1 SBRT combines multiple finely collimated radiation beams and stereotaxy (3D target localization). The multiple radiation beams intersect to deliver an accurate, high dose of radiation to a carefully defined location.

There are several terms that have been used interchangeably for SBRT. These terms include “stereotactic radiotherapy,” “fractionated stereotactic radiosurgery,” “hypofractionated stereotactic radiosurgery,” and “staged radiosurgery.” Consensus does not exist for the definition of SBRT with respect to a maximum number of radiation fractions, the minimum radiation dose per fraction, or the maximum number and diameter of lesions to be treated.2

SBRT is characterized by patient immobilization, limiting normal tissue exposure to high-dose radiation, preventing or accounting for organ motion (e.g., respiratory motion), the use of stereotaxy, and the subcentimeter3,4 accuracy of the delivered dose. The key components of a SBRT procedure are target delineation,5 treatment planning, and treatment delivery. The treatment team includes a radiation oncologist, medical physicist, radiation therapist, and depending on the body site and indication, a diagnostic radiologist, nurse, anesthetist, and dosimetrist as needed.6 Medical professionals, such as surgeons, may also play a role in the treatment team.

Scope

The goal of this Technical Brief is to provide a broad overview of the current state of SBRT for solid malignant tumors. The first draft included a review of SRS and SBRT treatment for all sites within the body (including spine and head) excluding the brain. However, based on the feedback of external reviewers and current working definitions of SRS and SBRT, the scope of this Technical Brief has been adjusted to focus on SBRT.

The definition of SRS developed by the American Association of Neurological Surgeons (AANS), the Congress of Neurological Surgeons (CNS), and the American Society for Radiation Oncology (ASTRO)is as follows:

Stereotactic radiosurgery is a distinct discipline that utilizes externally generated ionizing radiation in certain cases to inactivate or eradicate (a) defined target (s) in the head or spine without the need to make an incision. The target is defined by high-resolution stereotactic imaging. To assure quality of patient care the procedure involves a multidisciplinary team consisting of a neurosurgeon, radiation oncologist, and medical physicist.

Stereotactic radiosurgery (SRS) is typically performed in a single session, using a rigidly attached stereotactic guiding device, other immobilization technology and/or astereotactic image -guidance system, but can be performed in a limited number of sessions, up to a maximum of five.

Technologies that are used to perform SRS include linear accelerators, particle beam accelerators and multisource Cobalt 60 units. In order to enhance precision, various devices may incorporate robotics and real time imaging.7

The American Medical Association (AMA) has common procedural terminology (CPT) codes for SRS and SBRT that are recognized by the Centers for Medicare and Medicaid Services (CMS). According to the CPT codes, SRS treatment is delivered to a cranial lesion or spinal lesion consisting of one session (CPT codes: 77371, 77372, 77432, 63620); while SBRT has two applicable codes (77373 and 77435) with treatment delivery not to exceed five fractions within the body.8

This Technical Brief reports on the current technologies available to deliver SBRT; the 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 provide information about advances in the technology that are currently in development. This Technical Brief does not assess the quality of the retrieved studies or come to any conclusions about the reported results and adverse events.

Methods

Literature Searches

ECRI Institute’s biomedical engineers and medical physicists suggested confining our searches to the past five to eight years given the changes in the technology over time. Consequently, our search strategy for published studies involved Ovid, MEDLINE, EMBASE, the Cochrane Database, and the Health Technology Assessment Database from January 2000 to December 2010. The full search strategy can be found in Appendix A: Literature Search Methods.

We also searched the Internet for gray literature applicable to the Background section, Guiding Question 1 and Guiding Question 2. We performed the Internet searches in the Google search engine, and visited relevant links within the first 10 pages of search results. Gray literature was also searched within Windhover, Current HC News, Gray Sheet, The Wall Street Journal, and Clinica. We also visited association and organization Web sites (e.g., International RadioSurgery Association), and Web sites posted within each organization’s site. Information for instrumentation was captured by a search of the manufacturers’ Web sites and a search of the Food and Drug Administration’s (FDA) Center for Devices and Radiological Health (CDRH) (http://www.fda.gov/cdrh/). Instrumentation information can be found in Appendix F: Currently Marketed Devices for SBRT. Additional information on device specifications and compatible accessories was obtained through interviews with manufacturers (Appendix N).

Study Eligibility

Eligible studies were clinical studies of any design, published in English, with patient population of at least 3 patients, the use of SBRT, and with treatments delivered in 10 or fewer fractions. Studies not eligible for data extraction included treatment planning (e.g., dosing), treatment delivery (e.g., accuracy), nonmalignant tumors, the use of more than 10 treatment fractions, and fewer than 3 patients.

Guiding Questions and Findings of This Technical Brief

Guiding Question 1

1a. For which cancers has stereotactic body radiation therapy been used?

Based on our literature search, SBRT has been used for tumors located in the lung/thorax, thyroid, pancreas, liver, colon, uterus, pelvis, sacrum, kidney, prostate, and thyroid. The bulk of the studies identified in our searches were for tumors of the lung/thorax (k = 68).

1b. What are the theoretical advantages and disadvantages of stereotactic body radiation therapy compared to other radiation therapies that are currently used for cancer treatment?

Theoretically, SBRT’s most important features and reported advantages compared to other forms of external beam radiation therapy (EBRT) are the use of high-dose radiation, the delivery of one to five fractions within a few days (e.g., 2–3 days), decreasing the overall length of treatment, and an improved treatment response.5 Standard fractionated radiotherapy (e.g., 2D-CRT, 3D-CRT, intensity -modulated radiation therapy (IMRT)) are typically delivered in 25 –50 fractions, 5 days per week, for approximately 5 to 10 weeks. SBRT can be difficult to administer because of interfraction or intrafraction movements within the body (e.g., respiratory movements) and movements of the body.5

1c. What are the potential safety issues and harms of the use of stereotactic body radiation therapy?

As with other radiation treatments, geographic misses of the targeted tumor cause damage to surrounding healthy tissues. However, because each SBRT radiation fraction is a higher dose compared to other forms of EBRT, the potential for radiation injury is also higher.9 An essential part of SBRT is maintaining the delivery of the prescribed dose by strict quality control of the tumor images and the regular verification of the image sets.

Guiding Question 2

2a. What specialized instrumentation is needed for stereotactic body radiation therapy and what is the FDA status of this instrumentation?

SBRT can be delivered by dedicated and nondedicated linear accelerators. Advanced patient positioning, patient immobilization, multi-leaf collimators (MLCs) and micro -MLCs, x-ray tracking (stereotactic), advanced control systems, and treatment planning software are requirements for linear accelerator (linac)modification when performing an SBRT treatment. Nondedicated systems are capable of performing conventional radiation therapy, IMRT, along with SBRT, while dedicated systems are geared for SBRT treatments alone. SBRT can be delivered via a step and shoot method or dynamic delivery.5 Step and shoot delivery turns the radiation beam off when the gantry rotates to the next planned delivery angle. The use of dynamic delivery enables continuous delivery of the radiation beam by adjusting the MLC as the gantry rotates. Advantages of dynamic delivery include a decrease in treatment time, less organ movement during the treatment session, and an increase in patient throughput.5,10 SBRT devices are regulated by the FDA under the 510(k) process. To date there are 12 commercially available systems with identifiable features delivering SBRT treatments.

2b. What is an estimate of the number of hospitals that currently have the capability for stereotactic body radiation therapy in the United States?

We identified 384 facilities in the United States capable of performing SBRT in September 2009. An overall listing of these facilities, including specific body sites treated and devices employed can be found in Appendix J: Facilities Performing SBRT for Solid Tumors.

2c. What instrumentation technologies are in development?

The GyroKnife, manufactured by GammaStar Medical Group Ltd., is commercially available in the European Union having recently received the Conformité Européenne (CE) certification for European Union, medical devices.11 The device, featuring a Cobalt 60 radioactive source and two vertical rotating gyroscopes, currently awaits clearance by the FDA. It appears that this device has two configurations, linac-based x-rays or Cobalt (gamma) and has the potential to treat any organ in the body.

Guiding Question 3

Conduct a systematic literatures can for studies on the use and safety of SBRT in cancer, with a synthesis of the following variables:

3a. Type of cancer and patient inclusion criteria

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. Patient inclusion criteria commonly used in multiple studies across the different cancer types include inoperable tumors or patients refusing surgery; biopsy proven disease; a particular patient’s life expectancy; no prior RT or prior RT received in a particular time frame prior to SBRT; and a required level of performance on the Karnofsky or World Health Organization (WHO)/Eastern Cooperative Oncology Group (ECOG) scales.

3b. Type of radiation and instrumentation and algorithms used

Photon radiation was used in all included studies for SBRT treatment. The instrumentation reported in all studies included 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). Algorithms are used to plan and deliver treatment. The studies reported inverse treatment planning algorithms; pencil beam algorithms for dose calculation; and tissue maximum ratio calculation algorithms. Most of the studies described the device and photon energy, radiation beam angles, collimation technique, body immobilization technique, treatment planning imaging, treatment planning system/algorithm, tumor tracking, respiratory tracking/control, and image guidance during treatment. For more information, see Appendix M: Literature Results Device Specifications.

3c. Study design and study size

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.

3d. Comparator used in comparative studies

None of the published trials were comparative studies. We identified 50 ongoing SBRT trials (see Appendix K: Ongoing Clinical Trials). Only one of these trials involved a direct comparison of SBRT to a different form of radiation therapy. This trial commenced in April 2009 in France (NCT00870116), and is a nonrandomized comparison of SBRT delivered by CyberKnife versus SBRT delivered by linac versus conformational RT for treatment of non -small cell lung cancer (NSCLC). There are three other comparative trials which plan to use historical controls, one for metastatic breast cancer (NCT00167414), one in NSCLC (NCT00727350) and one in pancreatic cancer (NCT00350142). A lung cancer trial, based in the Netherlands (ClinicalTrials.gov identifier: NCT00687986), is a randomized trial comparing SBRT with primary resection of the tumor. The primary outcomes are local control, regional control, quality of life, and treatment costs. The enrollment target was 960 patients, and completion was expected in December 2013; however, the trial was terminated in April 2011 because of poor recruitment. Another trial being conducted in China (NCT00840749) will compare SBRT to surgical resection in NSCLC. The enrollment target is 1030 patients, with planned completion in 2013. Another trial (NCT00843726) being conducted in Roswell, NY, will randomize 98 patients to either one or three fractions of SBRT for treatment of NSCLC.

3e. Concurrent and/or prior treatments used

Prior treatments reported include surgery, radiation therapy (e.g., IMRT, brachytherapy), pharmaceuticals (e.g., tamoxifen), and/or chemotherapy. Some studies specified that prior radiation therapy or chemotherapy had to be completed within a certain timeframe before SBRT (e.g., 12 weeks). Chemotherapy was the concurrent treatment most often reported within the studies.

3f. Length of followup

We have 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]).

3g. Outcomes measured

The outcomes measured typically included tumor control or tumor response, toxicity, and overall survival. Overall cause-specific survival rates, overall survival, and disease-free survival rates were typically calculated using the Kaplan-Meier method. Most studies used the following four criteria to measure tumor control or tumor response: complete response, partial response, stable disease, and progression of disease.

3h. Adverse events, harms, and safety issues reported

Some of the most frequently reported adverse events include pain, fatigue, nausea, bleeding, and diarrhea. Some of the patients in these studies had prior cancer treatment and received SBRT for recurring cancers, and some patients had comorbidities.

Remaining Issues and Future Research Needs

Based on our literature searches, the studies published after 2000 were single-group prospective or single-group retrospective studies. We found 27 studies for tumors located in the pancreas, liver, colon, and fewer than 10 studies each for sites within the uterus, pelvis, kidney, prostate, and thyroid. These sites of treatment can be difficult to target, as there may be periodic (e.g., respiratory movement) or irregular (e.g., peristalsis) movement, or shrinkage of the tumor between fractionated treatments.

We did not identify any published randomized controlled trials (RCTs). Prospective controlled/comparative trials, preferably RCTs, are essential for establishing the relative safety and efficacy of SBRT in comparison to other methods of treatment. 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 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 efficacy of SBRT treatment.

References

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Fuss M, Thomas CR Jr. Stereotactic body radiation therapy: an ablative treatment option for primary and secondary liver tumors. Ann Surg Oncol. 2004 Feb;11(2):130–138. [PubMed: 14761915]
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Smink KA, Schneider SM. Overview of stereotactic body radiotherapy and the nursing role. Clin J Oncol Nurs. 2008 Dec;12(6):889–893. [PubMed: 19064382]
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Read PW. Stereotactic body radiation therapy: 2007 Update. Community Oncol. 2007 Oct;4(10):616–620.
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Miyamoto C. Chairperson & Professor, Department of Radiation Oncology, Temple University School of Medicine. Personal Communication. Feb 23, 2010. p. 51.
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American College of Radiology (ACR). Practice guideline for the performance of stereotactic body radiation therapy. Reston VA: American College of Radiology (ACR); 2004. p. 8.
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Barnett GH, Linskey ME, Adler JR, et al. Stereotactic radiosurgery–an organized neurosurgery-sanctioned definition. J Neurosurg. 2007 Jan;106(1):1–5. [PubMed: 17240553]
8.
Stereotactic radiotherapy (SRS)/stereotactic radiation therapy (SBRT) for Medicare plans Policy # SURGERY 0581 T3. Trumbull CT: Oxford Health Plans, LLC; Jan, 2009. [Accessed September 3, 2009]. Available at: https://www​.oxhp.com.
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Meyer JL, Verhey L, Xia P, et al. New technologies in the radiotherapy clinic. Front Radiat Ther Oncol. 2007;40:1–17. [PubMed: 17641499]
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Chen JC, Rahimian J, Girvigian MR, et al. Contemporary methods of radiosurgery treatment with the Novalis linear accelerator system. Neurosurg Focus. 2007;23(6):E4. [PubMed: 18081481]
11.
GammaStar’s Gyro Knife awarded EU certification. New York NY: Thomson Reuters; Apr 15, 2008. [Accessed November 25, 2008]. Available at http://www​.reuters.com​/article/pressRelease​/idUS130278+15-Apr-2008+PRN20080415.

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