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Commentary |
Physics Department, Clatterbridge Centre for Oncology, Bebington, Wirral, Merseyside CH63 4JY, UK
A meeting (Treatment Machine Commissioning–Changing the Culture) was held in London in November 2001 to discuss the implications of the recent injection of funding for radiotherapy equipment. Radiotherapy today has reached a point where technological changes have created the possibility of delivering higher therapeutic doses to more precisely targeted tissues and thereby increasing the potential for cure while simultaneously reducing the unwanted side effects. Although the original theme of the meeting related to treatment machine commissioning, the underlying questions are much wider. In what follows the author seeks to pull together some of these issues from the standpoint of medical physics. This commentary is a personal reflection on the issues raised at the BIR meeting, rather than a detailed report of the meeting.
Resource issues
Recruitment of clinical oncologists, physicists and radiographers has been a growing problem for some time. There are a number of contributing factors to this, ranging from the reduction in the birth rate to an increased demand for trained staff resulting from the newer treatment techniques which require more skilled staff time to plan and execute [1]. However, at the present time when there is a welcome increase in capital spending on radiotherapy equipment, the shortage of staff is particularly acute. Consequently, staff shortages have become the limiting factor in delivering the full benefits of the new equipment. These shortages are aggravated by delays in funding both training and substantive posts.
While a further increase in the number of medical physics training posts will be welcome, it is unlikely that this alone will match the increased demand. It is therefore necessary to find new ways to solve the problems. Three approaches seem worthy of consideration: more efficient ways of working, other routes of entry into the profession and ways of carrying out the tasks with less highly trained staff. The first of these will be the subject of subsequent sections of this paper. The second would seek to take advantage of the fact that the specifically medical aspects of a physicist's training are generally less than for doctors and radiographers. The more formalized training structures of recent years have made it more difficult for physicists from academia and industry to move into medical physics. The establishment of a well defined fast track system into medical physics should be a priority for government and the Institute of Physics and Engineering in Medicine (IPEM) alike.
Skills shortages among all staff groups in radiotherapy are promoting a fresh look at working practices. A well-balanced workforce requires physicists and radiographers with a broad training to lead the developments and to oversee safe treatment practices. However, there are many routine tasks in radiotherapy that can be carried out by staff with more task-specific training. Consideration of the role of radiography assistants is the subject of an ongoing pilot project, which is also looking at role development of radiographers at the other end of the scale. In parallel a much less structured development is the increasing creation of dosimetrist posts in a number of hospitals.
The concept of the dosimetrist is well developed in the USA and these staff are recognised as highly skilled professionals who specialize in treatment planning and dose measurement. While under the scientific supervision of medical physicists, this group of staff have a well-defined professional organization and career structure including the equivalent of advanced practitioner and perhaps consultant.
The whole process of identifying tasks that can be done by others can seem threatening to existing staff and often meets with resistance. This comes both from a feeling that the work being done is undervalued and a concern that such projects will lead to unemployment among existing professional staff. There are several ingredients that are essential for a successful skills mix programme. In the first place the skills mix development programme must be properly funded, including both set-up costs and the possibly increased on-going costs. While new staff are in training they will not be productive and will probably be a net drain on resources. Once they are trained it is possible that staff who are less qualified and less experienced will take longer to carry out the task and there will almost certainly be an increased need for supervision.
Radiotherapy is a complex and potentially dangerous process. If staff are allowed to carry out tasks without a full understanding of the scientific background, there is a danger that the occasional malfunction of software or hardware will go unnoticed. For example the dose rate of the beam of a linear accelerator does not directly determine the delivered dose provided that a dose rate independent dosimetry system is employed. However, sudden changes in dose rate are often associated with some fault in the accelerator, which may even prove catastrophic as was the case at Hammersmith in 1968 and in Poland in 2001. Likewise, inexperience was clearly a contributory factor to the treatment planning incident in Panama [2]. The considerably increased complexity of modern treatment methods requires careful attention to training requirements. To ensure that training courses concentrate sufficiently on what might go wrong is a daunting task which requires plenty of time for preparation of training as well as a very high level of understanding of the issues.
New approaches to treatment
A survey conducted in 1998 by McNee et al [3] showed that, at that time, use of three-dimensional planning techniques was restricted to relatively few patients in relatively few centres. Following the successful RTO1 dose escalation trial for prostate cancer, demand for conformal therapy has been increasing. It is often argued, with some justification, that there is little or no evidence that the more sophisticated treatment is beneficial. There are difficulties in providing such evidence which are of their nature hard to overcome. The acute side effects of prostate radiotherapy are apparently little affected by reducing the amount of normal tissue irradiated [4], but the late effects are significantly reduced [5]. Similarly, if survival is expected to be a number of years, it will take several years to demonstrate any survival advantage. The pressure to publish results within the 3 year time frame of most research grants means that longer term studies are difficult to conduct. An individual study may require follow up for up to 10 years before the data are fully mature and by this time treatment techniques may well have moved on. Associated with the greater culture of openness in medicine it has become increasingly difficult to recruit patients into some clinical trials.
Notwithstanding the difficulty of conducting trials, there is increasing evidence of a benefit from advanced radiotherapy. Non randomized studies have shown that prostate doses, which would have certainly led to massive complications, can now be given safely with minimal side effects [6]. Similar results have been obtained for lungs. The CHART (Continuous Hyperfractionated Accelerated Radiotherapy) trial [7] showed that small cell lung cancer is sensitive to modifications to the delivered dose with a difference of 20% between the control arm and the experimental arm.
At the same time there is evidence that waiting for treatment is detrimental to the outcome for many tumour types. If, as a result of giving more complex treatment, waiting times are increased, there may be a net detriment. This requires that treatment techniques are critically examined to ensure that any increase in the time taken to plan and deliver treatment can be expected to result in an improved outcome for the individual patient concerned.
New approaches to commissioning
At the meeting in November 2001 a number of suggestions were made to reduce the amount of time spent in commissioning. Walker [8] described how commissioning time for a matched Siemens accelerator at Newcastle had been reduced to a matter of a few weeks. During the manufacturer's set-up period, measurements had been made by the hospital staff to ensure optimum matching. An important contributory factor was that physics staffing levels at the time allowed the commissioning process to go forward without distraction, as there were other physicists available to cope with work demands elsewhere in the department. There was some discussion about whether the degree of matching was manufacturer dependent. The Elekta representatives present pointed out that matching to a standard chosen by the manufacturer was likely to be more successful than matching to an existing machine that may not have been set up to an optimum position originally. It is the experience in our centre that, unless the beams are matched extremely closely, the saving in time may be less than might be expected because of the requirement to resolve small differences. This may lead to a need to produce an averaged data set so that the work involved may even be greater. There is no doubt, however, that a common data set for a number of machines makes transfer of patients from one machine to another much easier.
A joint presentation from Bristol and Newcastle [9] looked at the possibility of creating a data set that would provide the beam data requirements for any treatment planning system. They presented a useful summary of the data requirements of different planning systems. The question therefore arises as to whether manufacturers could be persuaded to deliver all their accelerators matched to the same standard. The radiotherapy community could then create a national data set, which could be made available prepared for each treatment planning system. There are certain problems with such a system. Many centres wish to match their accelerator beams but they want to match them to the beam data already in use in their departments. For the reasons already discussed it is probable that the chosen beam data standard would not match existing linacs. There is also a problem of liability. No physicist would wish to take responsibility for the use of their beam data on another planning system in a different hospital. Equally most physicists would be reluctant to be responsible for the use of a data set that had been measured on another accelerator in a different hospital. There may also be an issue of how the additional work involved will be paid for. Of course, the measurement of beam data is only a small part of the process of commissioning an accelerator. Each centre must verify that the planning system calculates correctly when used to plan the particular treatment techniques in use in that centre. Various individual phantom measurements should therefore be made so that the exact planning methodologies can be verified.
In spite of these difficulties there may be a way forward. A considerable amount of the work of preparing beam data for a modern treatment planning system involves tuning the parameters in the beam model to fit the data. These fitting parameters are unlikely to be very different even if machines are not perfectly matched. For example in a number of treatment planning systems wedge filters are modelled by entering the physical shape of the wedge. However, such a model may not work first time and it may be necessary to adjust the computer representation of the wedge shape to fit the measured data. A system could therefore be set up whereby all centres with a particular planning system agreed to share their beam data with all other centres with the same or similar equipment. These data should be accompanied by reports of any comparisons already made by measurements. Any centre using such data would be committed to contribute any verification measurements and changes to the data made by the recipient centre. All centres would benefit from this by having sets of data from other centres to compare with their own. Even early adopters of a particular planning system would get some benefit as their data would be verified by others. (Anyone who would be willing to take part in such a scheme is invited to get in touch with the author.)
Quality control
The cost of carrying out quality control of treatment machines is considerable. This cost may be greater if quality control measurements are carried out during the working day. As already discussed, modern computer controlled accelerators may require fewer checks than older ones—although this may be offset by the need to carry out additional tests of newer features such as Intensity Modulated Radiotherapy (IMRT). The preface to IPEM Report 81 [10] made clear that it is the responsibility of the local physicist to assess the equipment in a particular centre to decide whether the normative tests and test frequencies recommended are appropriate for the local equipment. However, the report provided little or no direct guidance on what factors should be considered when deciding how to vary the recommendations. In the blame culture that seems to prevail with regard to radiation incidents, most physicists are likely to take the view that the personal risks associated with carrying out tests less frequently than recommended are too great. Following the meeting in November 2001, and in order to provide some support to the local physicists, a joint working party between the Royal College of Radiologists, the Institute of Physics and Engineering in Medicine and the College of Radiographers has been set up under the chairmanship of Dr Alan McKenzie. This group is tasked to attempt to identify methodologies to determine under what circumstances test frequencies may be reduced (or perhaps should be increased). This is a daunting task and early calculations suggest that the current recommendations may already be well founded.
Conclusions
The radiotherapy community owes it to patients to ensure that we make the best use of the limited resources at our disposal. At the present time these resources are limited more by the availability of trained staff than the availability of money. Inflexible funding arrangements and inflexible working practices by radiotherapy staff should not be allowed to get in the way of better patient care. All staff groups need to set aside the desire to promote their narrow group interest in order to work together for the good of the patient. These are fine words which assume that trust is built up between staff groups so that they all have the confidence to embrace new working practices without the concern that doing so will jeopardise their future working lives. The currently improving relationships between staff groups may be seen as a sign of hope for the future.
Received for publication December 12, 2002. Revision received March 28, 2003. Accepted for publication June 10, 2003.
References
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