Towards Safer Radiotherapy

Chapter 2: Nature and frequency of
human errors in radiotherapy
In any system errors are inevitable but, by understanding why they occur, systems can be put into
place to minimise their frequency and maximise detection before harm can be done. The actions
and failures of individual people play a central role, but their thinking and behaviour is strongly
influenced and constrained by their working environment and by wider organisational processes. 20
Major incidents almost always evolve over time, involve a number of people and a number of
broader contributory factors. For example, a change in a radiotherapy planning system without
matching changes to other procedures may unexpectedly result in an error being made when a
number of events converge many months later. 5 This scenario has been most clearly delineated in
Reason’s model of organisational accidents which provides the basis for a practical approach to
incident analysis (Figure 2.1). 21
Figure 2.1 Reason’s model of organisational accident
8
Organisation and
culture
Contributory
factors
Delivery
problems
Detection
systems
Management
decisions and
organisational
processes
Work environment
Team factors
Unsafe acts
✹
Individual factors
Task factors
Patient factors
Errors
Violations
Incident
Latent failures
Learning
Reproduced with the kind permission of BMJ Publishing
There is extensive literature on errors and their causes and it is not possible to cover all the issues
within this report. For a fuller account, the reader is referred to the Further Reading section on
page 77. When analysing incidents we can distinguish three key steps. First, one has to consider the
chain of events leading up to the incident, the narrative of events and problems. Second, one
examines this narrative to identify specific errors and problems that occurred during the process.
This report provides a template list of possible errors to aid this process. Third, one looks for the
causes of these errors that, in the terms of the framework, are referred to as contributory factors.
The identification of the process problems and contributory factors shows the vulnerabilities of the
system and provides the basis for safety enhancement and quality improvement initiatives discussed
later in the report.
Towards Safer Radiotherapy