DOS 516 - Week 2 Short Research Paper
Short Research Paper: Safety Trends and New Technology
The public perception of the safety of radiation therapy has been marred by several high-profile accidents involving accidental over- or under-dosing of patients during the course of the last few decades.1,2,3 These spectacular events have allowed practitioners and legislators to learn from mistakes and craft policies and laws that reduce the likelihood of future errors. Errors still persist, but improvements in technology in recent years have had an impact on their frequency and overall impact to patients.4
Princess Margaret Hospital in Toronto is one of the largest single-site radiation clinics in North America, with more than 7000 courses of treatment delivered every year.4 In a seven year retrospective analysis, the rate of radiation therapy incidents was tracked and correlated with advances in technology. In that period, Bissonnette & Medlam found that as IMRT began to replace wedge-based treatments, treatment accessory based errors declined 55%, mostly because IMRT technology was eliminating a potential source of errors. The adoption of IGRT decreased treatment location errors by 50% because it was possible to verify that a patient was set up in the correct position. While new technology helped in these areas, it also ended up resulting in a significant increase in documentation-based errors because the plans became ever more complex. These types of errors generally do not cause harm to patients, but they are still important to catch. Overall, the rate of errors fell from 2.0 to 1.2 incidents per 100 courses of therapy over the duration of the study.
In 2004, Princess Margaret Hospital began encouraging the reporting of near misses; cases in which an incident did not end up occurring because it was caught before it affected the patient.4 By encouraging the reporting of near misses, the pool of learning material expands and staff can identify areas where improvement can be made that might otherwise have gone unnoticed. In the period between 2004 and 2007, the rate of near miss reports varied between 0.1 and 0.02 per 100 courses.
The technology available in 2014 is much more advanced than that available in 2001-2007, and research into safety improvement continues. Technologies designed to assist in patient setup and position verification, such as electronic portal imaging devices (EPIDs), can be used in ways that they were not originally intended to be used. A team of researchers at Antoni van Leeuwenhoek Hospital in Amsterdam have developed a system by which EPID output data can be streamed continuously during treatment and analyzed to provide real time in vivo dosimetry.5 EPIDs are devices that can be mounted on a linac gantry directly opposite the treatment head, on the far side of the treatment table. This positioning allows measurement of the beam after it has already passed through the patient. This is an important distinction because the dose measurement system that tracks delivered MUs is positioned inside the head of the linac, upstream of the multileaf collimators (MLCs). In the case of an open-MLC accident such as occurred at St. Vincent's Hospital in Manhattan in 2005,3 the treatment would proceed until the correct number of MUs have been delivered, but much more dose would be delivered to the patient than expected because the MLCs were not in place to sculpt the beam into the correct shape, avoiding sensitive structures. If an EPID-based in vivo dosimetry solution were in place, it would immediately register dose in areas where it should not be, and it could initiate a shutdown command to the linac even before the first beam was fully delivered.5 This technology has already been tested on over 1200 patients.
Technology is not the only area where patient safety is improving. Human practice is governed by several sets of laws, as well as guidelines issued by industry organizations and accrediting agencies. The Joint Commission publishes a large set of National Patient Safety Goals which include sensible policies like requiring at least two patient identifiers when providing care to patients.6
Both technology designers and human practitioners continue to learn from past experiences, making radiation therapy safer over time. The incident rate is already low, and the majority of incidents that do still occur have very little or even zero impact on patients,4 but a culture built around safety wants to squash even these low-impact problems.
- Chustecka Z. Docs in prison after radiation overdose in prostate cancer. Medscape Website. http://www.medscape.com/viewarticle/778862. Published February 6, 2013. Accessed October 22, 2014.
- Rubin LS. The riverside radiation tragedy. Columbus Monthly Website. http://www.columbusmonthly.com/content/stories/2010/08/the-riverside-radiation-tragedy.html. Republished August, 2010. Accessed October 22, 2014.
- Bogdanich W. Radiation offers new cures, and ways to do harm. The New York Times Website. http://www.nytimes.com/2010/01/24/health/24radiation.html. Published January 23, 2010. Accessed October 22, 2014.
- Bissonnette JP, Medlam G. Trend analysis of radiation therapy incidents over seven years. Radiother Oncol. 2010;96(1):139-44.
- Hanson IM, Hansen VN, Olaciregui-ruiz I, Van herk M. Clinical implementation and rapid commissioning of an EPID based in-vivo dosimetry system. Phys Med Biol. 2014;59(19):N171-9.
- NPSG.01.01.01. The Joint Commission Website. http://www.jointcommission.org/assets/1/6/AHC_NPSG_Chapter_2014.pdf. Published 2013. Accessed October 15, 2014.