International Journal of Radiation Oncology * Biology * Physics
Volume 78, Issue 1 , Pages 3-10, 1 September 2010

Stereotactic Body Radiotherapy for Early-Stage Non-Small-Cell Lung Cancer: Report of the ASTRO Emerging Technology Committee

  • Mark K. Buyyounouski, M.D., M.S.

      Affiliations

    • Fox Chase Cancer Center, Philadelphia, PA
    • Corresponding Author InformationReprint requests to: Mark K. Buyyounouski, M.D., M.S., Department of Radiation Oncology, Fox Chase Cancer Center, Philadelphia, PA 19111. Tel: (215) 214-3707; Fax: (215) 214-1629
    • ,
  • Peter Balter, Ph.D.

      Affiliations

    • University of Texas, MD Anderson Cancer Center, Houston, TX
    • ,
  • Brett Lewis, M.D., Ph.D.

      Affiliations

    • Cancer Institute of New Jersey, New Brunswick, NJ
    • ,
  • David J. D'Ambrosio, M.D.

      Affiliations

    • Saint Barnabas Health Care System, Toms River, NJ
    • ,
  • Thomas J. Dilling, M.D.

      Affiliations

    • H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL
    • ,
  • Robert C. Miller, M.D.

      Affiliations

    • Mayo Clinic and Mayo Foundation, Rochester, MN
    • ,
  • Tracey Schefter, M.D.

      Affiliations

    • University of Colorado Health Services, Boulder, CO
    • ,
  • Wolfgang Tomé, Ph.D.

      Affiliations

    • University of Wisconsin, Madison, WI
    • ,
  • Eleanor E.R. Harris, M.D.

      Affiliations

    • H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL
    • ,
  • Robert A. Price Jr., Ph.D.

      Affiliations

    • Fox Chase Cancer Center, Philadelphia, PA
    • ,
  • Andre A. Konski, M.D., M.B.A.

      Affiliations

    • Wayne State University School of Medicine, Detroit, MI
    • ,
  • Paul E. Wallner, D.O.

      Affiliations

    • 21st Century Oncology, Inc, Moorestown, NJ

Received 30 March 2010; received in revised form 2 April 2010; accepted 2 April 2010. published online 20 July 2010.

Article Outline

 

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Introduction 

This report evaluates stereotactic body radiotherapy (SBRT) in the treatment of early-stage non-small-cell lung cancer (NSCLC). Stereotactic refers to precise positioning of the target volume in three dimensions. The target volume is usually localized by using some external frame of reference related to the treatment delivery system. The term “body” is used to distinguish the technique from treatments performed in the brain and skull base called intracranial stereotactic radiosurgery (SRS) or intracranial stereotactic RT (SRT). In contrast to SRS and SRT, SBRT requires special evaluation of and accounting of target motion in the absence of a reliable bony surrogate such as the skull. Stereotactic positioning is more precise than standard treatment immobilization processes, and as a result, SRS and SBRT commonly employ much higher doses per fraction and fewer fractions than conventional radiotherapy. Based on the definition of the SBRT method as approved by the Common Procedural Terminology (CPT) editorial panel, SBRT consists of a full course of treatment administered in five or fewer fractions. Because SBRT concentrates therapeutic doses of radiotherapy into a few, high-dose, highly conformal, precisely targeted treatments, it is a highly specialized technology that requires a significant quality assurance program in order to be effectively used to benefit patients. Given the scope of quality issues involved, the quality assurance program would need to address setup, testing, maintenance and interoperability of equipment, treatment planning, patient positioning, and process of care, as well as staffing, education, training, and appropriate supervision. While these aspects of SBRT are important, they are outside the scope of this paper.

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Description of Technology 

Introduction 

A basic, longstanding principle of radiotherapy is to maximize the dose of radiation delivered to a tumor and spare normal tissue in order to maximize tumor control while minimizing toxicity. In the case of SBRT for lung cancer, this maxim becomes ever more important because the geometry and/or intensity of the beams, rather than the differential radiosensitivities of normal and target tissues, is a predominant factor in sparing normal tissues. Therefore, an exact knowledge of the location and motion of the tumor is necessary to fully benefit from SBRT.

Tumors in the thorax can move a distance of up to 3 to 5 cm and, commonly, 1.5 to 2.5 cm with respiration 1, 2, 3, 4. Various methods have been developed to account for tumor motion including measuring and treating the entire track of tumor motion by using four-dimensional computed tomography (4DCT) for targeting 5, 6, 7, 8, applying abdominal compression to reduce motion 9, 10, gating the treatment to a specific portion of the respiratory cycle 11, 12, 13, active breathing control (14), and tracking the tumor with the radiation beam 15, 16, 17, 18.

Target localization and motion management 

A noninvasive body frame system has been developed that incorporates several features to ensure reproducible setup, including a vacuum bag that is fitted to the patient at the time of simulation, a scale that facilitates reproducible positioning of the patient in the frame, an abdominal compression paddle to restrict abdominal motion, and external fiducial markers to improve setup accuracy 19, 20. This system is particularly useful when the patient is to be imaged in one room, and the entire patient/body frame system is moved to the treatment room. Without a body frame, either implanted fiducial markers or in-room volumetric imaging is required for accurate internal soft tissue-based setup.

Respiratory gating, which activates the radiation beam only when the tumor is at a predetermined location in the respiratory cycle, can be used to account for respiratory motion 11, 12, 21, 22. The use of gating requires some measure of the tumor location within the respiratory cycle, which can be done directly but is more often done through some respiratory surrogate such as abdominal distension or diameter. Spirometry has also been used to gate based on tidal volume (23).

Alternative motion management techniques include dynamic gating and breath-hold techniques. With dynamic gating, patients are permitted to breathe regularly, sometimes with audio or visual coaching, and the radiation beam is activated only when the patient reaches predetermined points in the respiratory cycle. The breath-hold technique is similar, in that the radiation beam is activated only when the target is at a predetermined point in the respiratory cycle. However, the patient is coached to hold his or her breath at a specific phase of the respiratory cycle, usually with the aid of visual feedback based on abdominal distension or tidal volume. The breath-hold can be either voluntary or assisted with an occlusion valve. Compared to dynamic gating, breath-hold allows for volumetric imaging, stabilization of the radiation beam, and expansion of the lungs to provide more distance between the target and nearby critical structures.

Gating is performed with real-time or near-time verification of the target position in the gate with in-treatment room imaging. Two commercially available systems dedicated to this purpose are Novalis/Exactrac (BrainLAB, Feldkirchen, Germany) (24) and Cyberknife (Accuray, Sunnyvale, CA) (25), which have room-mounted orthogonal x-ray systems that can localize radioopaque fiducial markers implanted in the tumor, which is based on early work of Shirato et al. (26). A Cyberknife can also directly image and track the target depending on the size and location of the tumor. Tumor tracking with these systems can be accomplished with the use of external fiducials.

A 4DCT can be used to address issues of respiratory motion for non-stereotactic dedicated systems (7). A 4DCT can be constructed using a multislice CT scanner combined with a respiratory surrogate to develop a series of 3DCT scans, each representing a different respiratory phase, to determine an envelope of tumor motion. This structure can be expanded to include areas of subclinical disease, resulting in an internal target volume (27).

The most common form of motion management used in many centers with experience and in Radiation Therapy Oncology Group (RTOG) studies has been chest wall breathing with abdominal compression. Chest wall breathing exerts forces on the intrathoracic tissues in multiple opposing directions in contrast to the mostly craniocaudal force vectors associated with diaphragmatic breathing. As a result, the amplitude of tumor motion with chest wall breathing can be significantly decreased. With this technique, the patient is first coached to expand the lungs using the upper chest wall rather than by moving their diaphragm toward their abdomen. This technique is feasible but somewhat unnatural when not under physical exertion. To help “remind” the patient to use primarily chest wall breathing, a firm but tolerable pressure plate is applied to the upper abdomen to inhibit abdominal diaphragmatic motion. Numerous reports show that this technique can reliably dampen target motion to under 1 cm, even for targets close to the diaphragm 20, 28.

Treatment planning 

The high degree of conformality associated with SBRT can be achieved by implementing multiple, nonopposing, and often noncoplanar beams or arcs, spread over a large solid angle with fairly equal weighting to minimize the entrance dose and ultimately the volume of the irradiated normal tissue (29). The number of beam directions and the relative beam weights are the entrance dose and that should be kept to a modest level to prevent potential severe skin or chest wall toxicity while keeping a uniform isotropic dose fall-off (30). In the assessment and evaluation of dosimetric properties of SBRT plans, three major criteria are considered: conformity index, high-dose spillage, and intermediate-dose spillage. The conformity index is defined as the ratio of the volume of the isodose shell that provides planning tumor volume (PTV) coverage of 95% to the PTV volume. It is recommended that this ratio be kept to less than 1.2 to minimize the volume of normal tissue receiving an ablative dose. Any areas receiving greater than 105% of the prescription dose, commonly referred to as high-dose spillage, are generally confined to the PTV. Intermediate-dose spillage, which is responsible for most of the toxicity associated with SBRT, is evaluated using one or both of the following methods, as follows: (1) by keeping the dose to any point 2 cm away from the PTV surface below a limit that is a function of PTV volume, and/or (2) by defining the region of intermediate-dose spillage as the ratio of 50% isodose coverage to the PTV volume. These concepts have been used in all of the RTOG multicenter lung cancer treatment studies to date, and constraints as a function of target volume can be viewed in the radiotherapy sections of these protocols (RTOG protocols 0236, 0618, 0813, and 0915 [http://www.rtog.org/members/active.html#lung]).

An additional challenge in treatment planning for small lesions in the lung parenchyma is the lack of electronic equilibrium. Many methods for determining dose distributions assume that each dose calculation point is in an area of electronic equilibrium (i.e., that the amounts of scatter entering and leaving this area are the same). This is, generally, not true when irradiating small lesions surrounded by air space in the lung. Various treatment planning systems have been compared to Monte Carlo calculations 28, 31, 32 and measurements (33). Only convolution superposition algorithms were found to have good agreement for these types of tumors. These algorithms are commercially available from at least two manufacturers (Pinnacle, Philips Medical Systems, Madison, WI; and Eclipse AAA, Varian Medical Systems, Palo Alto, CA). Treatment planning software based on Monte Carlo calculations (MultiPlan, Accuray, Sunnyvale, CA) is also available. Photon pencil beam algorithms should be avoided for treating areas of electronic disequilibrium (34).

Treatment delivery 

Several commercially available units, which have been presented previously (35), can deliver SBRT including Novalis (Brain LAB AG, Feldkirchen Germany), Tomotherapy HiArt (Tomotherapy, Madison, WI), Varian Trilogy (Varian, Inc., Milpitas, CA), Elekta Synergy-S (Elekta, Inc., Norcross, GA), Siemens Primatom (Malvern, PA), and Cyberknife (Accuray, Sunnyvale, CA).

Summary 

Lung SBRT requires the ability to precisely determine the location and extent of motion of tumors, to be able to develop complicated 3D treatment plans under nonequilibrium conditions and to deliver high dose with great geometric precision. This can be done effectively with some existing CT simulators, treatment planning systems, and linear accelerators but requires a great deal of care on the part of the treatment team.

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Description of Patients Potentially Benefiting From Use of Technology 

Rationale for lung SBRT for early-stage disease 

Medically inoperable lung cancer 

Early-stage (stage I/II) NSCLC is typically managed with definitive surgical resection, but some patients are unfit for surgery due to underlying medical comorbidities, such as cardiopulmonary disease related to chronic smoking. Medical inoperability is regarded as the presence of comorbid illnesses that renders the patient at higher than acceptable risk of surgical morbidity and mortality (36).

Medical inoperability is generally defined as either poor pulmonary function based on objective criteria (baseline forced expiratory volume in 1 second [FEV1] <40% predicted; postoperative predicted FEV1 <30%, predicted; diffusion capacity, <40%, predicted; baseline hypoxemia [≤70 mmHg] and/or hypercapnia [≥50 mmHg] or exercise oxygen consumption, ≤50%, predicted) or as specified by a thoracic surgical oncologist (37). Contraindications to surgery may include severe pulmonary hypertension, diabetes mellitus with severe end-organ damage, severe cerebral, cardiac, or peripheral vascular disease, or severe chronic heart disease. Any one of these criteria may preclude surgery.

Despite the often severe competing risk of death from other causes in these patients, McGarry et al. (38) have shown that the risk of dying from lung cancer can still exceed 50%, favoring aggressive treatment. Historically, conventional radiotherapy consisting of 6 to 7 weeks of daily treatment has been considered the standard of care for this group (39). A large systematic review of an estimated 2,003 medically inoperable patients with stage I/II NSCLC receiving radiotherapy alone showed complete response rates ranging between 33% and 61% and local failure rates between 6% and 70% (40). Better response and survival rates were seen in patients with smaller tumors and in those receiving higher doses. Lung SBRT has the potential to deliver high radiation doses to these patients and to minimize exposure to surrounding lung and normal tissues, all while reducing overall treatment time.

Operable lung cancer 

For patients who are surgical candidates but refuse surgery, SBRT provides a nonoperative treatment alternative. Radiation dose escalation has been proposed to improve outcome for these patients that can be achieved easily with SBRT 41, 42, 43.

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Description of Patient Risks From Technology 

Higher doses in fewer fractions using SBRT may result in less normal tissue repair than conventional fractionation and therefore greater toxicity. The much smaller treatment volume used with SBRT may offset these concerns by exposing less normal tissue. However, smaller treatment volumes could compromise local control if smaller volumes compromise target coverage.

These relative risks associated with SBRT, compared to conventional fractionation, can be estimated using the linear quadratic model. However, it is critical that caution should be exercised in making such extrapolations since the linear-quadratic equation was chosen for its ability to model effects of dose fractionation only within the conventional treatment range; no additional compensation is made for the fact that large dose fractions in this range may lead not only to enhanced tumor cell killing but also to ablation of the underlying microvasculature (i.e., changes to the efficacy of reoxygenation) and other factors supporting tumor growth, further enhancing radiotherapy efficacy and/or toxicity 44, 45, 46, 47, 48.

Ideally, the safety and efficacy of SBRT for lung cancer will be defined by clinical trials that vary SBRT dose fractionation and prospectively collect outcomes. Single-institution and multiinstitution trials have been conducted that provide an understanding of the risks associated with some dose fractionation schedules. Future studies will, hopefully, provide newer and better understandings of the mechanisms and effects of SBRT.

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Evaluation/Summary of Results of Existing Studies 

Single institutional experiences 

North America 

At Indiana University, a phase I trial was conducted in which doses were escalated in 6-Gy increments, starting at 24 Gy in three fractions for 47 medically inoperable, early-stage patients (49). The maximum tolerated dose was not reached in stage T1 patients, but was 66 Gy in three fractions for stage T2 patients. Local recurrence occurred in 10 of the 47 patients, nine instances of which occurred at doses of ≤48 Gy (in three fractions).

A subsequent phase II trial treated 70 patients with T1 disease with 60 Gy in three fractions and T2 disease with 66 Gy (50). The two-year local control rate was 95%. The median overall survival was 33 months. Eight of the 70 patients developed grade 3 to 4 toxicity (using Common Terminology Criteria for Adverse Events [CTCAE]) including pneumonia, pleural effusion, apnea, skin reaction, and decline in pulmonary function tests. Six patients died as a result of toxicity. High-grade toxicity (grade, ≥3) was predicted by tumor location on both univariate and multivariate analyses, with hilar/pericentral locations having higher rates of toxicity than peripheral locations. There were six treatment-related deaths, all in patients with central tumors.

An M.D. Anderson Cancer Center study reported preliminary SBRT results for stage I (n = 37 patients) and isolated peripheral recurrent (n = 22 patients) NSCLC (8). Patients received 50 Gy in four fractions. With a median follow-up of 10 months, all patients had a complete response, partial response, or stable disease (control rates were not reported). There were no cases of grade 2 or higher radiation pneumonitis in the stage I patients. Of the total, 10% of patients had grade 2 dermatitis.

A Staten Island University Hospital study published results of 75 patients treated with SBRT (51). Patients were either medically inoperable or refused surgery and had various stages of disease. Sixty-seven patients received stereotactic radiation alone, and 8 patients received conventional radiotherapy prior to receiving a stereotactic radiotherapy boost (which would not actually qualify as SBRT based on the CPT definition). The median total radiation dose was 40 Gy, and the fraction size was 8 Gy. With a median follow-up of 17 months, 2-year overall survival was 45%. Complete response radiographic response was reported in 7 patients, partial response in 25 patients, stable disease in 22 patients, and progressive disease in 9 patients. Toxicities reported were radiation pneumonitis in 2 patients, acute nausea and vomiting in 1 patient, pleural effusion in 2 patients, and pneumothorax in 1 patient.

The Fox Chase Cancer Center conducted a Phase I trial in which doses were escalated in 8-Gy increments, from 40 Gy to 56 Gy in four fractions 52, 53. Seventeen of 18 patients had NSCLC (1 with metastatic rectal cancer), 4 of whom were treated for an oligometastasis. Three patients developed symptoms from therapy; with only 1 patient (48 Gy) who had grade 3 disease; this patient developed bacterial pneumonia 2 days after treatment that was assumed to be radiation related. With a mean follow-up of 17 months, the 1-year local control rate was 97%, and the 18- month local control rate was 93%. No late pulmonary complications have occurred. No patient had a decrease in FEV1 or diffusioning lung capacity for carbon monoxide at 1 month after treatment. The maximum tolerated dose was not reached during this study.

Asia 

Yoon et al. (54), in Korea, reported results of SBRT for primary (n = 21 cases), recurrent (n = 17 cases), or metastatic (n = 53 cases) lung tumors (54). Dose was escalated over time from 30 Gy in three fractions to 40 Gy in four fractions and ultimately to 48 Gy in four fractions. With a median follow-up of 14 months, the 2-year progression-free survival rate was 81%. The 2-year overall survival rate was 51%. There were no grade 3 (CTCAE) or higher pulmonary complications, and acute treatment-related toxicity was deemed “negligible.”

A Kyoto University phase I/II trial reported using 48 Gy in four fractions for 45 early-stage NSCLC patients (27 medically inoperable, 18 refused surgery) (55). For stage IA patients (median follow-up, 30 months), the 5-year local relapse-free survival rate was 95%, the disease-free survival was 72%, and the overall survival was 83%. For the stage IB patients (median follow-up, 22 months), there were no local failures. The combined 5-year disease-free survival rate was 71%, and the overall survival rate was 72%. There was a 4% rate of symptomatic pneumonitis requiring steroids.

Europe 

In Sweden, the Sahlgrenska University Hospital treated 45 medically inoperable, early-stage NSCLC patients to 45 Gy in three fractions (56). With a median follow-up of 43 months, 9 patients (20%) developed a local recurrence or had local persistence of disease. Three-year overall survival was 55%, with a median survival of 39 months. The 3-year lung cancer-specific mortality rate was 67%. Four patients (9%) had grade 1 esophagitis, and 4 patients had transient chest pain. Late toxicity developed in 2 patients who had rib fracture and 3 patients who developed significant atelectasis.

In Denmark, 40 medically inoperable stage I NSCLC patients were treated with 45 Gy in three fractions in a phase II study (57). Actuarial 2-year progression-free survival was 54%, cancer-specific survival was 62%, and overall survival was 48%. There was only 1 local failure. There were 4 grade 3 to 4 (World Health Organization [WHO] criteria) cases of dyspnea, and 2 patients with grade 3 chest pain.

Zimmermann et al. (58), from Munich, Germany, treated thirty medically inoperable stage I NSCLC patients with 37.5 Gy (range, 24–37.5) in 3 to 5 fractions. Most patients (69%) received 37.5 Gy in 3 fractions. With a median follow-up of 18 months, 2-year local control was 87%. Two-year disease-free survival was 72%. There were 2 regional failures (7%) and 5 distant failures (17%). Overall survival at 2 years was 75%. Acute toxicity (CTCAE) consisted of 1 grade 3 pneumonitis, and late toxicity consisted of 1 rib fracture.

Pulmonary toxicity 

Henderson et al. (59) studied 70 patients treated with SBRT (60–66 Gy in three fractions) and found no association between decreasing baseline lung function and survival and concluded that poor lung function should not preclude patients from SBRT. Following treatment, Ohashi et al. (60) reported no significant decline in total lung capacity, vital capacity, or FEV1 in 15 patients 1 year from completion of SBRT (50 Gy in five fractions). Paludan et al. (61) examined various dosimetric parameters but were unable to identify a relationship between SBRT (45 Gy in three fractions) and dyspnea (WHO criteria). Furthermore, there was no temporal relationship between dyspnea and treatment.

Follow-up evaluations 

The natural history of radiographic findings after SBRT for lung cancers remains an area of active investigation (62). The Hiroshima group (63) characterized CT findings after SBRT and found acute (<6 months) “diffuse consolidation” correlated with grade 2 (CTCAE) acute radiation pneumonitis. Fluorodeoxyglucose (FDG) avidity is expected to decline following SBRT (64) and appears to decline exponentially (65). However, FDG avidity may not be entirely specific as some authors have shown that it may remain elevated for 12 to 24 months without evidence of progression on CT (66).

Multiinstitutional trials of SBRT for lung cancer 

RTOG protocol 0236 was a Phase II trial of SBRT (60 Gy in three fractions) for medically inoperable stage I/II NSCLC. With a median follow-up of 24.8 months, 3 patients (5%) were scored with a local failure, giving an estimated 2-year local control rate of 93.7%. No patients experienced regional failure, while 8 patients (15%) experienced distant failure. Two-year estimates of disease-free survival was 66.6%, and overall survival was 72.0% (67).

RTOG is also investigating SBRT in the operable setting in RTOG protocol 0618, a phase II trial of SBRT for medically operable patients with clinical stage I/II NSCLC. Medical operability in this trial is defined strictly. A qualified thoracic surgeon must determine that there would be a high likelihood of obtaining negative surgical margins and that the patient must have good pulmonary reserve (FEV1, >40% predicted; estimated postoperative FEV1, >30% predicted; diffusion capacity, >40 % predicted; absent hypoxemia and or hypercapnia, exercise oxygen consumption, >50 % predicted) and no major comorbid illnesses. Adjuvant chemotherapy is recommended. Early stopping rules and frequent evaluation with opportunity for salvage surgery have been incorporated. Results of this trial are also eagerly awaited.

Single-fraction stereotactic radiotherapy to lung tumors 

A study from Stanford University (68) reported a phase I trial in which patients (81% underwent reirradiation) were treated with doses ranging from 15 to 30 Gy in a single fraction. The 1-year freedom from local progression was 91% for patients who received >20 Gy and 54% for those who received less (p = 0.03). In a German study (69), 58 patients received 30-Gy single-fraction SBRT and, with a minimum of 1-year of follow-up, 94% of primary lung tumors were controlled locally. In Japan, 59 lung tumors were treated with a single-fraction 20- to 34-Gy dose, and the 2-year local control was 83% for tumors treated to at least 30 Gy and 52% for those who received a lower dose (70). A single 20-Gy fraction was used at the University of Pittsburgh, and, with a median follow-up of nine months, 22% of patients had an initial complete response, and an additional 31% of patients had a partial response, with 28% demonstrating stable disease (71).

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Future Prediction Based on Technology Development 

With the continuing development of tumor tracking technologies, it may be possible to further reduce the target size through margin reduction. This could have the potential to reduce both early and late unwanted side effects by reducing the amount of normal tissues irradiated by high dose. As criteria mature for tumor size, total dose, fractional dose, and normal tissue dose limits, SBRT for NSCLC may become a routinely viable option for these patients. The American Society for Therapeutic Radiology and Oncology (ASTRO) supports ongoing clinical trials such as those being conducted by the RTOG to further define efficacy and toxicity of fractionated and single-fraction SBRT for lung cancer.

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Analysis and Technology Assessment Findings 

Technological advancements such as the development of a body frame with external fiducial markers, respiratory gating, and breath-holding techniques, cone beam, 4DCT, and robotically assisted linear accelerators allow for increasingly smaller treatment volumes through the implementation of stereotactic lung radiotherapy. Careful selection for small, inherently demarcated tumors, located typically in the periphery of the lung, away from sensitive normal structures such as the heart and proximal tracheobronchial tree, permits the use of multiple, noncoplanar beams and allows for a rapid reduction in dose beyond a few millimeters outside the tumor target volume. Multiple clinical trials throughout the world have shown successful escalation of the biologically effective dose while limiting normal tissue toxicity with doses in the range of 48 Gy in four fractions to 60 to 66 Gy in three fractions 49, 50, 51, 52, 55, 56, 57, 58. Tolerability of treatment and local control has been excellent in single-institution reports in both the medically inoperable and operable settings. In the medically inoperable setting, we conclude that SBRT is an accepted treatment option for stage I/II NSCLC (72). In the operable setting, we conclude more study and longer follow-up are necessary to ensure that results are equivalent to those of surgery. Ideally, medically operable patients with stage I lung cancer would likely receive SBRT on a structured investigative protocol. By and large, tumor location has been a concern since Timmerman et al. (50) have demonstrated an increased risk of mortality with centrally located tumors. However, others have successfully treated central tumors, albeit with a more fractionated approach. Single-fraction SBRT may require more careful patient selection and, based on the research to date, would likely be conducted only in the setting of a clinical trial.

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Emerging Technology Committee Note 

Assignment of this project to the Task Group was made on April 20, 2008, and data collection for preparation of the full report available on the ASTRO website and this condensed version was closed on May 29, 2008. Clinical, physics, and biology data and regulatory revisions available after that date are not included in this review.

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Disclaimers and Notifications 

This document was prepared by the Emerging Technology Committee (ETC) of the American Society for Radiation Oncology.

•Prior to initiation of this evaluation project, all members of the ETC and the Task Group performing the evaluation were required to complete conflict of interest statements. These statements are maintained at ASTRO headquarters in Fairfax, VA, and any pertinent conflict information will be published with the report. Individuals with disqualifying conflicts are recused from participation in ASTRO emerging technology assessments.

•The primary role of the ETC is to provide technology assessments regarding emerging technologies to various stakeholders within and outside the Society. It is not the role of the Committee to develop or defend code definitions, valuation recommendations, or other payment policy development functions.

•ASTRO emerging technology reports present scientific, health, and safety information and may to some extent reflect scientific or medical opinion. They are made available to ASTRO members and to the public for educational and informational purposes only. Any commercial use of any content in this report without the prior written consent of ASTRO is strictly prohibited.

•ASTRO does not make or imply any warranties concerning the safety or clinical efficacy of the devices reviewed in this report. ASTRO assumes no liability for the information, conclusions, and findings contained in its Emerging Technology reports.

•ASTRO regards any consideration of its technology assessment reports to be voluntary, with the ultimate determination regarding any technology's application to be made by the practitioner, in consultation with the patient, in light of each patient's individual circumstances in accordance with applicable law. Decisions regarding coverage of a technology, device, or procedure are made by payers and government agencies in accordance with applicable legal standards and their decision-making processes. In addition, this technology assessment describes the use of devices or procedures; it cannot be assumed to apply to the use of these interventions performed in the context of clinical trials, given that clinical studies are designed to evaluate or validate innovative approaches in a disease for which improved staging and treatment are needed or are being explored. In that assessment development involves a review and synthesis of the latest literature, a technology assessment also serves to identify important questions and settings for further research.

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 Conflict of interest: none.

PII: S0360-3016(10)00528-6

doi:10.1016/j.ijrobp.2010.04.010

International Journal of Radiation Oncology * Biology * Physics
Volume 78, Issue 1 , Pages 3-10, 1 September 2010

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