A study on human error, safety culture and risk in radiation oncology

Abstract

In 2010 the New York Times wrote a series of articles on different radiation procedures including radiotherapy treatments. These articles highlighted a number of incidents that have occurred in the course of radiotherapy treatment and brought these incidents into the lime light.

A review of the literature indicates that safety is becoming an increasingly high priority in radiotherapy. However, there are gaps in the literature. Locally recorded incident rates are reported by individual hospitals, but there is no study looking at reported incident rates in multiple hospitals.

A number of high profile incidents highlighted the contribution of patient safety culture to incidents. This is notable with the Orthovoltage incident in Ottawa, Canada and the incident in Epinal, France. In the study described in this thesis recorded “incidents” were evaluated, with emphasis on where the incident initiated, the type of incident that occurred and the human influence on the event. Radiotherapy departments across Ireland were asked to submit their locally recorded incidents and near-misses. The department setup, including the staffing numbers and patient numbers, were analysed to look at the variation between departments.

Patient safety culture, in the context of this thesis, refers to the attitudes, values and actions of staff members to different aspects of patient safety. The patient safety culture was evaluated in multiple radiotherapy departments using the Agency for Healthcare Research and Quality, Hospital Survey of Patient Safety Culture. Twelve metrics of patient safety culture were examined. The results of the overall patient safety grade were compared to the reported incident rates. There is an indication that there is a relationship between incident rates and safety culture. However the low number of radiotherapy sites examined and the variation in procedures for identifying incidents means it is not possible to statistically prove this. To prove this with a statistical power of 0.8, a sample size of 85 is required. The variations in how departments identify incidents also creates a level of uncertainty in reference to incident rates.

The results from the review of incidents indicated that the majority of incidents could be attributed to human error. A proactive risk assessment model was developed using process mapping, probabilistic risk assessment and human error analysis to evaluate process safety.

The human error probability was calculated using the Standardized Plant Analysis Risk Model Human reliability analysis (SPAR-H). Error mode block diagrams were developed and the fault tree analysis techniques were used to evaluate the effects of errors on the other tasks in the process. For a standard prostate treatment with ultrasound guided daily setup, the predicted mean incident rate was 0.11.

In a situation where the stress of a staff member was rated higher than normal the mean is 0.24. For the head and neck model this is 0.17 and 0.48 respectively. This thesis successfully evaluates patient safety culture and incident rates in radiotherapy. The proactive risk assessment technique developed as part of this thesis can be used as a template for radiotherapy departments to adhere to recommendations from the AAPM TG-100 and the new EU directive that recommends proactive risk assessment techniques in radiotherapy.