Room: AAPM ePoster Library
Purpose: Stereotactic radiosurgery (SRS) was historically delivered at a small number of facilities using specialized equipment and techniques. Today, more than half of radiotherapy facilities in the US are delivering SRS. Such rapid proliferation of a complex technique raises concerns regarding practitioner expertise, commissioning, and adherence to established quality assurance guidelines. The current widespread use of complex delivery techniques using conventional linacs, including single-isocenter multi-target VMAT, represents a significant increase in planning and delivery complexity and warrants additional attention. AAPM TG-119 facilitated a standardized approach to IMRT commissioning and evaluation, addressing the rapid implementation of IMRT and low pass rates on credentialing tests. We characterize the current state of SRS and advocate for a TG-119 equivalent test suite for SRS commissioning.
Methods: We evaluated SRS practice patterns in the US and results from Imaging and Radiation Oncology Core (IROC) SRS phantom irradiation to identify current shortcomings and/or needs related to commissioning and quality assurance in SRS.
Results: Over 1,000 facilities in the US currently deliver SRS. This number increased by 60% from 2004-2014 and currently includes nearly 500 dedicated SRS systems. The percentage of patients treated using linac-based SRS increased from 3% to >30% from 2003-2011 and continues to increase. In 2013, tolerances for the IROC SRS phantom became 5%(point dose), and 85% gamma pass(5%/3mm). From 2013-present, phantom pass rates are 83% and 93% for linac and Gamma Knife, respectively.
Conclusion: IROC SRS phantom results reveal a substantial fraction of facilities failing to meet relatively lenient dosimetric tolerances for a relatively simple target. Numerous high profile treatment deviations associated with SRS delivery have already occurred. We propose that a standardized SRS planning and dosimetry comparison, including a suite of complex and clinically relevant plans, would improve our ability to accurately deliver SRS, and potentially mitigate future quality and safety incidents.
Stereotactic Radiosurgery, Commissioning