Often, the limiting dosimetric factor associated with conventional spine radiotherapy is the dose to the spinal cord. Conventional external beam radiotherapy lacks the precision to deliver large single-fraction doses of radiation to vertebral tumors near radiosensitive structures such as the spinal cord. Although short term pain control may suggest high rates of partial response, the complete response rates may be sub-optimal. Spine radiosurgery allows for the ability to better shape the radiation around the critical structures such as the spinal cord and effectively dose escalate while still maintaining safe dose limits to the spinal cord and other surrounding organs at risk (for example the esophagus, bowel, etc.). It is postulated that precise confinement of the radiation dose to the treatment area, as is the case for intracranial radiosurgery, should increase the likelihood of successful tumor control and clinical response at the same time that the risk of adjacent neurological injury is minimized [1–3, 7, 15, 18, 20, 33–36]. It is this premise upon which the widespread adoption of radiosurgery for the treatment of spine and paraspinal tumors has been based.
With the increasingly widespread adoption of intensity-modulated radiotherapy (IMRT) combined with imaged guided techniques to allow for stereotactic body radiotherapy treatments, there has been increasing attention focused on the safety of these highly complex technologies. Initially, attention focused on the ability of centers to plan IMRT effectively. External audits of dosimetric comparisons between three-dimensional conformal radiotherapy (3D-CRT) and IMRT plans were performed and published . While most clinical studies that demonstrated to yield superior conformality of the target volume and avoidance of critical structures in treatment plans were conducted in academic centers with rich experience in IMRT, it is less clear if these same dosimetric gains seen by IMRT over 3D-CRT can be seen at all centers. One major concern is the reproducibility of target volume delineation by clinicians who lack significant clinical experience. Radiation oncologists may not be formally trained and cognizant of the anatomy related to the spine and paraspinal structures . One published external audit confirmed that a more experienced center is more able to maximize the dosimetric advantages of IMRT . These authors went on to recommend that future efforts should be directed toward addressing this learning curve by establishing protocols, conducting educational workshops, and fostering institutional mentorship programs or communications to close the gap between experienced and less-experienced centers. The International Spine Radiosurgery Consortium has published consensus guidelines for target volume definition in spinal stereotactic radiosurgery for common clinical situations in an effort to decrease the potential for contouring variability among clinicians in this regard .
The American Society for Therapeutic Radiology and Oncology (ASTRO) and the American College of Radiology (ACR) have put forth guidelines for the performance of IMRT , IGRT  and SBRT . These guidelines were published as an educational tool designed to assist practitioners in providing appropriate care of patients. The guidelines for SBRT specifically address the qualifications and responsibilities of personnel, including the radiation oncologist, medical physicist, radiation therapist, and “other participants” (e.g. surgeons). The authors state that strict protocols for QA must be followed. SBRT requires levels of precision and accuracy that surpass the requirements of conventionally fractionated radiation therapy or conventional IMRT. The SBRT process requires a coordinated team effort between the radiation oncologist, the medical physicist, the medical dosimetrist, and the radiation therapist. These inclusive guidelines also address issues of quality control and improvement, safety, infection control, patient education, documentation, and follow-up recommendations. A more recent scope of practice guideline was published by CARO that focused on spine, lung and liver SBRT. This document also clarified the role of the radiation oncologist, departmental considerations prior to implementation of an SBRT program and QA measures to be considered for a safe program. However, no recommendations are offered regarding the institutional credentialing of personnel involved in the delivery of SBRT . The current manuscript focused on the training aspects of the credentialing process for spine radiosurgery. Our questionnaire did not address other phases of the credentialing process such as planning exercises and phantom testing such has been described elsewhere [29, 30].
Several position statements have been published regarding quality assurance needs for modern image-based radiotherapy such as radiosurgery. Once such report summarized the consensus findings of a joint symposium of the ASTRO, the American Association of Physicists in Medicine (AAPM), and the National Cancer Institute (NCI) . The recommendations from this body focused largely on the development of more appropriate proscriptive quality assurance tests (QA) for these newer SBRT delivery systems. Healthcare administrators need to assure the presence of appropriate personnel and ancillary equipment resources, as well as capital resources, when new advanced RT technology modalities are implemented. The pace of formalized clinical physics training must rapidly increase to provide an adequately trained physics workforce for advanced technology RT. Finally, government and private entities should support research directed toward addressing QA problems in image-guided RT therapies. While this consensus statement made specific recommendations regarding QA guidance for SBRT, they failed to address the issue of institutional training and credentialing of personnel.
Much of the initial focus for credentialing for SBRT related to quality assurance issues in conducting multi-institutional advanced technology clinical trials . The first such work began in 2002 when the Radiation Therapy Oncology Group in North America began the process of developing multicenter prospective trials in lung cancer using SBRT . These activities have had an impact not only on the treatment received by patients enrolled in clinical trials, but also on the quality of treatment administered to all patients treated in each institution. Such techniques have now been adopted globally .
Several cooperative groups have determined that the technologies used in certain clinical trials are sufficiently advanced to warrant specific credentialing of institutions that wish to participate in these trials . The many challenges in credentialing institutions and participants for multi-institutional clinical trials in SBRT have been reviewed. The primary goal of credentialing is to reduce the deviation rate of data submitted to clinical trials. Credentialing offers a number of other benefits. Chief among these is the education of staff at the participating institution to ensure an understanding of the protocol and its goals. Cooperative groups have experienced deviation rates that sometimes amount to as much as 17% of the cases submitted . A report by the National Cancer Institute Work Group on Radiotherapy Quality Assurance described the redesigning of radiotherapy quality assurance that included opportunities to develop an efficient, evidence-based system to support clinical trials . The group made four recommendations for the improvement of multi-institutional clinical trial QA that might decrease these relatively high deviation rates.
While professional organizations and government sponsored agencies have published guidelines regarding credentialing for radiosurgery, these recommendations were once again within the context of multi-center government sponsored clinical trials. The National Cancer Institute-sponsored Advanced Technology Quality Assurance Consortium pioneered the development of an infrastructure and QA method for advanced technology clinical trials that requires volumetric digital data submission of a protocol patient’s treatment plan and verification data . The quality assurance of imaged-guided radiation therapy (IGRT) within clinical trials is currently in its early stages, but its importance will continue to grow as IGRT becomes more widely adopted. The outcome of clinical trials may be affected by a known wide degree of variation in dose delivery of IMRT across multiple sites . Compared to conventional radiotherapy, the steep dose gradients and tight margins achieved with IMRT have an even greater probability of leading to detrimental consequences via reduced tumor control and increased toxicity. The IGRT component of clinical trials that includes sophisticated planning and treatment protocols must undergo stringent QA. For this reason, IMRT QA is an essential part of the credentialing process for clinical trials.
The ultimate goals of the process of credentialing of personnel are for patient safety and quality of care. Areas of strong agreement summarizes the areas for which there is strong agreement among institutions for the process of spine radiosurgery credentialing. These areas might be considered the minimum requirements necessary for the safe and effective implementation of a new spine radiosurgery program. Areas of some agreement summaries the areas for which there is some agreement among institutions for the process of spine radiosurgery credentialing.
Quality outcomes are now being assessed by private payers and professional societies. These outcomes are also more readily available to patients. Differences in quality assessed through registry initiatives may drive the professional societies, health care institutions, or payers to mandate a more rigorous credentialing process for clinicians providing high technology services such as spinal radiosurgery. Relatively few studies have been undertaken to address the specific issue of credentialing of personnel within an individual institution. Njeh et al. supported that radiation departments should be certified to proven new technologies such as IGRT . Radiosurgery has become part of formal neurosurgery resident education in the United States . There are also calls for better coordination between surgeons and radiation oncologists in the cancer treatment decision-making process for spine and other primary tumor sites . Furthermore, already there are published recommendations of conjoint statements by professional and governing organizations on credentialing and delineation of privileges for therapeutic procedures using radiopharmaceuticals . To our knowledge, no such statements have been made regarding credentialing and delineation of privileges for extracranial radiosurgery, including spine radiosurgery.
The current survey study revealed that there is an important need for guidance regarding the credentialing of physicians and staff for the participation in the treatment of spine radiosurgery at an individual institution. Broad agreement exists among experienced spine radiosurgery centers in the areas of policies and procedures, training requirements, surgeon involvement, and the role of industry and professional organizations in the credentialing process. Strong agreement in the credentialing processes was observed despite the multi-national nature of the consortium, which consists of members from the United States, Canada and Germany. Furthermore, all institutions feel strongly regarding the importance of such credentialing in the development of a safe and effective spine radiosurgery program.