Radiation oncologists use more than a dozen quality assurance (QA) checks to prevent radiotherapy errors, but until recently, the Johns Hopkins researchers say, no one had systematically evaluated their effectiveness.
Working with researchers at Washington University in St Louis, the Johns Hopkins team gathered data on about 4,000 “near miss” events that occurred during 2008-2010 at the two institutions. They then narrowed the data set to 290 events in which errors occurred that – if they had not been caught in time – could have allowed serious harm to patients. For each commonly used QA check, they determined the percentage of these potential patient-harming incidents that could have been prevented.
The group’s key finding was that a combination of approximately six common QA measures would have prevented more than 90 per cent of the potential incidents.
“While clinicians in this field may be familiar with these quality assurance procedures, they may not have appreciated how effective they are in combination,” says Eric Ford, assistant professor of radiation oncology and molecular radiation sciences at Johns Hopkins.
Ionizing radiation such as gamma radiation or proton beam radiation has long been a staple in cancer treatment, because it can efficiently create cell-killing DNA breaks within tumours. The goal is to use it in ways that maximize the dose delivered to a tumour, while keeping healthy tissue around the tumour as protected as possible by sharply focusing the radiation treatment area.
Unfortunately, the multistep complexity of radiation therapy, and the numerous precision measurements its use entails, can sometimes lead to mistakes, with patients getting too little radiation where it’s needed, or too much where it isn’t.
One QA check, a piece of hardware called an Electronic Portal Imaging Device (EPID), is built in to many radiotherapy-delivery machines, and can provide a real-time X-ray-like image of the radiation coming through a patient. But Eric Ford says less than one per cent of radiotherapy clinics use EPID because the software and training needed to operate are mostly absent.
However, Eric Ford says, their research showed that another key to safety turned out to be a humble checklist of relatively low-tech measures, “assuming it’s used consistently correctly, which it often isn’t.” The checklist includes reviews of patient charts before treatment by both physicians and radiation-physicists, who calculate the right dose of radiation.
Use of film-based radiation-dose measurements as an alternative to EPID and a mandatory “timeout” by the radiation therapist before radiation is turned on to double-check that the written treatment plan and doses match what’s on the radiation delivery machines were also on the list of the most effective QA procedures.
A common QA measure known as pre-treatment IMRT (intensity modulated radiation therapy), in which clinical staff do a “test run” of the radiotherapy device at its programmed strength with no patient present, ranked very low on the list – because it would have prevented almost none of the potential incidents studied. “This is important to know, because pre-treatment IMRT often consumes a lot of staff time,” says Eric Ford.