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Hidden danger, obvious opportunity: error and risk in the management of cancer

Department of Surgery and Molecular Oncology, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, UK

Correspondence: A J Munro, Department of Surgery and Molecular Oncology, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, UK. E-mail: a.j.munro{at}dundee.ac.uk

"Radiotherapy: Hidden Danger": the digested read

• Radiotherapy is useful but it can be dangerous.
  
• Here are a few anecdotes illustrating these dangers.
  
• The main one concerned something that happened 25 years ago – but it's a dramatic story so I will include it anyway.
  
• People involved in treating patients with radiotherapy should be very, very careful.
  
• The procedures and processes involved in clinical radiotherapy are quite complicated, and mistakes can occur at any link in the chain from diagnosis to follow-up.
  
• People who practise radiotherapy should be trained to do it properly and should be aware that mistakes can occur.
  
• Doctors should take seriously the possibility that mistakes can occur and should not be frightened of being blamed if mistakes happen.
  
• There is international interest in the problem of errors in radiotherapy.
  
• Measuring the dose received by each patient (in vivo dosimetry) should become routine in radiotherapy in the UK.
  

In March 1896, Alan Archibald Campbell Swinton claimed that, according to his experiments, X-rays did no harm. A few weeks later, Elihu Thompson proved him wrong. Thompson, who with Thomas Alva Edison had founded the General Electric Company, irradiated his own hand and produced severe dermatitis. Shortly thereafter, Edison's assistant Clarence Dally developed severe radio-dermatitis and, despite the amputation of his arm, died in 1904 from radiation damage. We have always been aware that radiation has the capacity to do both harm and good and, from its very inception, those concerned with the speciality of radiotherapy have been aware of the potential risk to patients arising from treatment. There has been a culture of safety and protection in radiotherapy for over 100 years.

The Chief Medical Officer (CMO) for England and Wales has recently produced a report entitled "Radiotherapy: Hidden Dangers" [1]. Much of the content of the CMO's report comes as no surprise to most of us. The report deals with the very "warp and woof" of our culture and daily practice. What is somewhat surprising, however, is the tenor of the report and some of its conclusions (see text Box).

The tone of the report may, to many physicists and radiotherapists who have been involved in quality assurance, seem more than a little patronising, particularly since, up until recently, there has been little central promotion of the culture of safety. Most of the initiatives that have ensured that clinical radiotherapy is as safe as it now is have come from within the professions involved. Much of the work put in, in a world driven by waiting-time targets, has been effectively unfunded. The majority of UK radiotherapy departments signed up to formal programmes of quality assurance in radiotherapy (QART) [2] and ISO 9000 long before the NHS published its Manual of Cancer Services. Attention has finally been paid and, although no-one has been acknowledged for their efforts so far, perhaps we should regard the attention itself as a form of gratitude.

Any detailed consideration of the CMO's report on errors in clinical radiotherapy needs to consider the following issues: the cultural background against which the report is set; the definitions we are going to use when considering errors and adverse events; the scale of the problem and the risks of error; the magnitude of risk compared with other activities in both clinical practice and everyday life; the risk compared with any benefits achieved; what we might do to reduce the known and unknown hazards; and how we might identify the unknown hazards. Of most relevance for UK practice, we need to consider the resource implications of introducing measures such as in vivo dosimetry (IVD) routinely into clinical practice.

	Patient safety — context and background

Top Patient safety -- context... The taxonomy of medical... Risks have to be... Errors in radiotherapy: the... Radiotherapeutic errors in the... The role of in... Reducing known errors,... Conclusions References

 
Clinicians have, since the very beginning of clinical practice, regarded the safety of patients as one of their most important responsibilities. There is nothing particularly new in the concept of patient safety, except perhaps that we are now naming and analysing something that previously was simply regarded as an intrinsic part of medical care. Why the sudden recent interest? James Carville had the answer: "the economy, stupid".

In 2000, the Institute of Medicine in the US published a report, "To Err is Human", on medical errors in the US hospital system [3]. The report starts with two startling anecdotes, one of which concerned a prominent journalist who was treated with a fatal chemotherapy overdose, but quickly moves on to consider the fiscal consequences of medical error. The report estimated that adverse drug events were costing the US economy $2 billion per year in hospital costs alone, and killing 7000 Americans (1000 more than were being killed in industrial accidents).

In the same year, the NHS produced a similar report — "An Organisation with a Memory" [4]. Interestingly, the estimate of the annual cost of errors was, on a pro rata basis, much higher — £2 billion. The estimate of adverse events causing harm to patients was 10% of all hospital admissions. The NHS at that time was paying about £400 million per year to settle claims of clinical negligence, and had a potential liability for a further £2.4 billion's worth of claims. The report made no mention of radiotherapy but did consider, in some considerable detail, the problem of inadvertent administration of intrathecal vincristine.

The realization that errors cost money has led to a series of centrally driven initiatives to eliminate errors in clinical practice.

	The taxonomy of medical mistakes

Top Patient safety -- context... The taxonomy of medical... Risks have to be... Errors in radiotherapy: the... Radiotherapeutic errors in the... The role of in... Reducing known errors,... Conclusions References

 
We need to be absolutely clear about our language. Our words should mean exactly what we want them to mean: no more, and no less. In addition, we should all agree on what those meanings are. At present, all is chaos [5]: my "error" is your "incident", which may, or may not, be her "adverse event".

No contextual or numerical analysis of errors is possible until we formally define what we mean when we use the term "error". We also, when considering any classification system, need to consider the uses to which the information generated will be put. Different consumers will have different needs. Patients will primarily be concerned with errors that would have a clinical impact, i.e. errors that would decrease the effectiveness or increase the toxicity of treatment, whereas those concerned with quality assurance would want to know about any and every error, regardless of clinical impact.

There are several systems currently under development for classifying clinical errors. The Joint Commission on Accreditation of Healthcare Organizations (JCAHO) classification [6] recognizes five root nodes: impact, type, domain, cause and prevention/mitigation. The World Health Organization (WHO) is currently building on the JCAHO patient safety event taxonomy to produce an international classification of patient safety [7].

Ekaette et al [8] published a taxonomy of the terminology associated with risk analysis and radiation treatment. They define five domains: assessment, prescription, preparation, treatment and follow-up. They then define terms to describe the things that can go wrong: incident, misadministration, adverse event and error. They define the root event as the incident: "an unwanted or unexpected change from normal system behaviour that causes, or has the potential to cause, an adverse event". Incidents are then subclassified as sporadic or systematic, as concerned with process or concerned with infrastructure.

I see no particular reason why, simply because of its complexity, radiotherapy should require its own specific taxonomy. We need to co-opt the best of the existing taxonomies for our specific use. Not only does this imply that we will be clearly understood by our colleagues in other clinical disciplines, but it also means that any radiotherapeutic errors, when viewed as part of the healthcare system as a whole, will be firmly placed in their correct perspective.

	Risks have to be put into perspective

Top Patient safety -- context... The taxonomy of medical... Risks have to be... Errors in radiotherapy: the... Radiotherapeutic errors in the... The role of in... Reducing known errors,... Conclusions References

 
Life is intrinsically dangerous; we all face risks every day. It is useful, therefore, to try to put risks into perspective using some common unit of currency so that direct comparisons can be made. One simple way to do this is simply to convert risks to a rate per million. As such, Table 1 covers risks associated with medicine in general, and also includes, for comparative purposes, some estimates from everyday life.

	Errors in radiotherapy: the scale of the problem

Top Patient safety -- context... The taxonomy of medical... Risks have to be... Errors in radiotherapy: the... Radiotherapeutic errors in the... The role of in... Reducing known errors,... Conclusions References

 
There is extensive literature on this topic: over 1400 Medline references on errors, quality assurance and radiotherapy. The vast majority of this literature has been produced by radiotherapists, physicists and radiographers. There is little evidence of any input from administrators, managers or experts in public health or risk assessment.

These papers are by no means the only source of information. The United States Nuclear Regulatory Commission reports incidents involving isotopes, but not those involving linear accelerators (http://www.nrc.gov/reading-rm/doc-collections/event-status/ event/en.html). The International Atomic Energy Agency (http://rpop.iaea.org/RPoP/RPoP/Content/InformationFor/HealthProfessionals/2_Radiotherapy/AccidentPrevention.htm) provides data on incidents involving errors in clinical radiotherapy and has published several detailed reports of specific incidents [13–15]. There is also a database (ROSIS) based in Lausanne of self-reported incidents (http://www.clin.radfys.lu.se/default.asp). The WHO is also involved in assessing error rates and setting standards. The WHO World Alliance for Patient Safety has set up a group in January 2007 whose remit is to investigate and set standards for avoiding "harm to patients caused by radiotherapy" (http://www.who.int/patientsafety/activities/technical/radiotherapy/en/print.html). Unfortunately, as there is no uniform nomenclature and because there is no definition of the components for a minimum dataset concerning patient safety in clinical radiotherapy, it is not easy to reduce the information from these various data sources into a common metric.

There have been two major reports on preventing accidental exposures in clinical radiotherapy: one from the International Commission on Radiological Protection (ICRP) [16] and one from the International Atomic Energy Agency (IAEA) [17]. The latter report mentions in vivo dosimetry only once, as an example of "defence in depth". The ICRP report estimated that 30% of errors in external beam radiotherapy involved incorrect calibration of beams; 28% were due to errors in treatment planning and dose calculation; and 20% were due to errors in treatment set-up and delivery. Problems with equipment and maintenance accounted for 13% of the 46 accidents that they were able to investigate in detail.

The likelihood of clinically evident damage arising from a radiotherapeutic error is dependent upon two key probabilities: the probability of an error occurring and the probability of harm arising from any given error. The American Association of Physicists in Medicine (AAPM) recognize this latter issue and, based on a simple classification used by the Food and Drug Administration (FDA), propose the following classification [18]: a Type I hazard is a condition that could lead to death or serious injury; a Type II hazard involves only a minimal risk of serious injury. The AAPM system subdivides Type I into Class A (life-threatening complications) and Type B (increased probability of unacceptable outcome, but no threat to life). A Class A incident involves an overdosage of >25%; a Class B error involves an underdosage or overdosage of between 5% and 25%. These percentages apply to the whole course of treatment.

One problem is that it may take time for the adverse effects of treatment to become manifest and, in the meantime, the patient may have succumbed to their disease. This will bias the assessment of harm: long-term problems are more likely to be identified in patients with breast cancer than in patients with lung cancer. All this is superimposed upon a considerable amount of heterogeneity: biological dose, prescribing conventions, dose distribution, individual susceptibility, follow-up, ascertainment and attribution of events to causes. There is, therefore, unlikely to be any clear-cut relationship between the rate of error and the incidence of adverse effects in clinical radiotherapy.

Table 2 summarizes, again using risk per million, the recent data on errors and harm arising from clinical radiotherapy using modern radiotherapeutic techniques and equipment. Overall, errors not discovered until after treatment has started occur at a rate of around 20 000 per million courses of radiotherapy (about 10% of the rate of safety incidents in the UK hospital system as a whole [10]). Errors with significant clinical consequences are much rarer, occurring (depending upon definition) at a rate of between 1000 and 10 000 per million courses of treatment.

The risk of death arising as a direct consequence of radiotherapeutic error seems to be very low indeed: less than 5 per million courses of treatment, which is equivalent to the risk of developing new-variant Creutzfeldt–Jakob disease (CJD) in those who ate beef during the UK bovine spongiform encephalopathy (BSE) epidemic, and about one-third of the risk of dying (per million flight hours) as a result of a non-commercial flight in the US. The risks are there, but in terms of many other risks people are prepared to take, they are comparatively small. An important point is that skydivers and passengers in light aircraft generally have no other immediate threat to their existence. Patients attending for radiotherapy do. Overall, their risk of dying from cancer is 690 000 per million courses of radiotherapy. Patients are therefore more than 69 000 times more likely to die from cancer than they are to die from an error associated with their treatment. I am not arguing here that this makes such errors unimportant, far from it. Any premature death, whether from radiotherapeutic error or from cancer, is a human tragedy and no such loss should ever be belittled. I am simply trying to bring a sense of perspective to the question of the relative importance of errors in radiotherapy.

	Radiotherapeutic errors in the context of cancer treatment

Top Patient safety -- context... The taxonomy of medical... Risks have to be... Errors in radiotherapy: the... Radiotherapeutic errors in the... The role of in... Reducing known errors,... Conclusions References

 
Any patient facing major surgery for cancer knows that things can go wrong; they understand that they may not survive their operation or the period immediately thereafter. They know that their surgeon will not deliberately harm them, yet they also know that errors of judgement can occur and that sometimes the clinical problem is beyond the technical competence of the clinical team. Surviving the operation is only the beginning of another period of high risk due to deep vein thrombosis, vulnerability to infection and other post-operative complications. The data in Table 3 give some indication of the risk of dying following major surgery for cancer. Surgeons, in common with radiation oncologists, have a long tradition of publishing their statistics on morbidity and mortality and, despite recent managerial claims to the contrary, there has always been a culture of learning from experience and not simply repeating the same mistakes. Medline contains over 2000 references to quality assurance or post-operative mortality in relation to surgery for cancer, and 150 of these references come from the UK. Interestingly, medical oncologists appear to show no such interest in publishing on the topic of safety and quality assurance. There are only 463 Medline references on quality assurance or errors involving chemotherapy for cancer. 188 of these references deal with the quality assurance aspects of radiotherapy in studies involving both modalities, leaving only 275 references dealing with errors, quality assurance and chemotherapy for cancer.

The reasons for this lack of apparent interest are complex but may, in part, stem from a difference in culture. When you come from a background of using desperate remedies to treat desperate diseases, then safety issues concerning the administration and prescribing of the drugs you are using may pale into insignificance compared with the intrinsic dangers of both the disease and the treatments being used. Table 3 summarizes the available data on prescription and administration errors in relation to chemotherapy for cancer. It is curious that, although the processes involved in prescribing and administering chemotherapy are much simpler than the analogous activities in radiotherapy, the error rates are as high as those for radiotherapy. There are approximately 100 parameters to be specified for a course of 6 cycles of chemotherapy, compared with over 1000 parameters for a 6-week course of conventional radiotherapy [16]. Error rates for chemotherapy administration are consistently over 5000 per million prescriptions. There is only one exception: a small recent study with computer-based prescribing that had an error rate of zero; the clue to this unusual occurrence may lie in the authors' declaration of potential financial conflicts of interest [21].

There is a growing literature concerning the fallibility of computer-based prescribing systems [22–25]. We need to be aware, when prescribing either radiotherapy or chemotherapy, that computerization may solve some problems but at the expense of producing new sources of error. Current computer systems do not yet incorporate the fuzzy logic and Bayesian analyses that may, in part, compensate for the deficiencies of traditional linear computer software programming. There may be important lessons here. Computerization may engender a false sense of security and, at the same time, increase the opportunities for error. Caveat emptor applies. We should still crosscheck manually using first-order approximations and, if the computer output does not roughly agree with our estimates, then we need to check again.

In summary, the risk of patients being harmed as a result of errors in the prescribing and administration of radiotherapy is, in relative terms, remarkably low. The risks are substantially less than those associated with major surgery, considerably lower than those arising from the admission to hospital, and, allowing for relative complexity, somewhat less than those occurring during cancer chemotherapy.

	The role of in vivo dosimetry

Top Patient safety -- context... The taxonomy of medical... Risks have to be... Errors in radiotherapy: the... Radiotherapeutic errors in the... The role of in... Reducing known errors,... Conclusions References

 
To advocate IVD as being a desirable safety precaution is one thing [1, 26, 27], to deliver IVD as a routine quality assurance procedure for clinical radiotherapy in the UK is quite another matter [28]. The CMO's report is vague on detail — we are assured that IVD offers a potential solution to the perceived problem of high error rates in radiotherapy, but we are given no details as to any strategy for implementing such a service. Many centres already use IVD, based on thermoluminescent dosimetry or diodes, for special techniques such as total body irradiation or when a vulnerable normal tissue, e.g. the eye, is close to a field edge [29]. I assume that the CMO expects us to do more than this, but it is unclear how much more. We have a fairly straightforward way of making first-order estimates of what might be involved.

Workload data and projections gathered in Scotland and also in England and Wales [30, 31] give us a basis upon which to work. By going back to the original source material upon which these recent reports have been based [32–46], it is possible to calculate separately the number of radical and palliative courses of radiotherapy required each year in the UK and then to use these figures, combined with recommendations on fractionation [47], to estimate the total number of fractions and fields required in each category. The assumptions used in calculating machine time, physicists' time and oncologists' time were estimated using data provided in the ESTRO [48] and AAPM [49] reports on in vivo dosimetry, and are summarized in Table 4. Table 5 and Figure 1 give examples of several possible strategies and their implications. The financial cost of implementing IVD as routine is, given the current shortage of equipment and specialist staff in the NHS, less important than the person time and machine time consumed. When people and machines are in short supply, financial costs cease to be a limiting factor and the opportunity cost in terms of treatment delays becomes the most important issue.

View this table: [in this window] [in a new window]   Table 4. Assumptions made in calculating the estimates shown inTable 5

View larger version (12K): [in this window] [in a new window]   Figure 1. A graphical summary of the data presented inTable 5. (A) IVD on every field on each patient on each day of treatment; (B) IVD on all radical fields each day and palliative fields weekly; (C) IVD on all fields weekly on every patient; (D) IVD on all fields weekly on every patient treated radically; (E) IVD on all fields for first fraction only — all patients; (F) IVD on all fields for first fraction and if any plan change thereafter; (G) IVD on all fields for first fraction only — radical patients only; (H) IVD on all fields for first fraction only — radical patients only and if any plan change thereafter; (I) IVD on all fields for first fraction only (random 10% of patients); (J) IVD on all fields for first fraction only (random 10% of radical patients); (K) IVD used only for complex or unusual plans; (L) IVD used only in special circumstances, e.g. total body irradiation, eye dose etc. Equiv, equivalent; wte, whole time equivalent.

IVD is, in any event, no panacea; nor is it the only way of detecting mistakes in a timely fashion [52]. Common errors are those related to misplacement of fields or shielding, or to reversal of collimator dimensions. These would be more readily detected by portal images than by IVD. However, it is the errors that you cannot find that you should be worrying about. Systematic errors in planning systems are of particular concern. If a plan suggests that the exit dose from a given field should be 40 Gy per fraction, then clearly there is something quite wrong and it should not require IVD to detect the problem. It is the more subtle errors that are worrisome. Consider a faulty plan that predicts an entrance dose of 1.2 Gy per fraction when the correctly planned dose should be 0.9 Gy. This is within the plausible range and no one would raise an eyebrow at a dose reading over 1.2 Gy for IVD on an entrance field. Unfortunately, the error here is (in relative terms) considerable, i.e. 33%, and the false reassurance caused by the acceptable diode reading could mean that the plan itself is never adequately checked. If the wrong plan predicts the wrong dose, then the ability of IVD to measure the wrong dose correctly is of little interest or consequence.

	Reducing known errors, identifying unknown errors

Top Patient safety -- context... The taxonomy of medical... Risks have to be... Errors in radiotherapy: the... Radiotherapeutic errors in the... The role of in... Reducing known errors,... Conclusions References

 
As soon as we start to consider reducing the risks of error in clinical radiotherapy, we enter the territory so memorably staked out by Donald Rumsfeld: "Reports that say that something hasn't happened are always interesting to me because, as we know, there are "known knowns"; there are things we know we know. We also know there are "known unknowns"; that is to say, we know there are some things we do not know. But there are also "unknown unknowns" — the ones we don't know we don't know". We can devote considerable effort to eliminating known sources of error, and we can work out a means to trap errors arising from known unknowns, but it would be foolish to pretend that the unknown unknowns do not exist.

The QART process [2] and compliance with ISO 9000 standards (http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber = 42180) give us some confidence that safety systems and procedures within radiotherapy departments in the UK are rigorous and well defined. We do not yet have the problem that affects some other countries in the developed world, i.e. the rinky-dink stand-alone facility, operated for profit and without proper procedures and safeguards. We should not be complacent, but cross-checking of plans, portal films, double signatures and similar precautions go some considerable way to protect against catastrophic error. The study from Princess Margaret Hospital, Toronto, [53] showed that approximately 27 000 errors per million prescriptions were detected before patients started treatment.

When there is a skin reaction to observe, clinicians can recognize dose differences of around 5% [54]. It is undoubtedly more difficult to detect dose differences in the absence of an anticipated skin reaction but, in pelvic radiotherapy, clinicians can detect increased toxicity associated with dose increases of between 7% and 10% [16]. Overall, the available evidence suggests that differences of between 5% and 10% in absorbed dose can be detected clinically [55].

Changes in working practices may influence the clinical detection of dose discrepancies. With the advent of nurse- and radiographer-led on-treatment review clinics, many trainees in radiotherapy no longer see, on a day-to-day basis, acute reactions related to treatment. We are producing a generation of uncalibrated oncologists. It is likely that assessments performed by radiographers and nurses will be meticulous and robust, but will they be heeded and will they be put into a clinical context? There is a strong argument to be made for IVD using patients rather than diodes. As with chemotherapy, patients could keep daily diary cards in which, using a simple scoring system, they record their subjective experience of key symptoms related to their radiotherapy. These subjective observations could be combined with weekly objective assessments based on the CTAEv3.0 scores (http://ctep.cancer.gov/forms/CTCAEv3.pdf) for the appropriate treatment-related toxicities. The scores could be routinely collected and analysed in real time using web-based systems via PDA, laptop or static terminal [56–58]. Locally collected data could be analysed centrally. Any systematic deviation in the severity of toxicity associated with standard radiotherapeutic techniques, whether within a department or between centres, would be immediately apparent. This approach, unlike diode-based dosimetry, would have value beyond simply estimating dose. We would learn a great deal about the subjective experience of radiotherapy, about individual variation in response to radiation and about the effectiveness (or ineffectiveness) of remedies routinely used in managing radiation-related side-effects [59]. Such data, collected prospectively and nationally, would go far beyond error trapping and, given the known variations in practice [60], would provide a rich resource for clinical radiation biology and supportive care.

	Conclusions

Top Patient safety -- context... The taxonomy of medical... Risks have to be... Errors in radiotherapy: the... Radiotherapeutic errors in the... The role of in... Reducing known errors,... Conclusions References

 
Based on the information I have presented in response to the CMO's report, I would make the following modest proposals:

1. We need to develop a web-based open knowledge space for the rapid exchange of information concerning problems and errors. This should contain:
   
2. 1. information, based on a nationally agreed taxonomy and compatible with international patient safety reporting systems [7], on how to define, classify and code incidents involving therapeutic radiation
      
   2. an incident reporting form that provides all information for direct entry into a database which incorporates the minimum dataset necessary for collating and assessing information on incidents of various types
      
   3. a running report, available via the open knowledge space, on all known errors and incidents (including near-misses) occurring in UK radiotherapy
      
   4. automatic email alerts to clinical directors and principal physicists throughout the UK whenever an incident is reported
      
   5. links to the relevant literature and to national and international reports on errors and incidents in radiotherapy
      
   6. a Wiki (an editable on-line document that can be changed by anyone with access to it) or similar text-based resource so that experience can be efficiently and rapidly shared
      
   
   
3. We need a formal evaluation of the cost-effectiveness of various strategies for using IVD as a method for detecting errors in clinical radiotherapy. The rigorous methodologies developed by the Health Technology Assessment (HTA) Programme and National Institute for Health and Clinical Excellence (NICE) provide excellent examples of how this might be approached. We should not simply assume that because IVD is a good thing, it is necessarily a worthwhile use of resources. The concept should be evaluated with the rigour that we would apply to any other unproven intervention.
   
4. We should be prospectively recording, and collecting centrally, information on the toxicity experienced by each individual treated with radiotherapy in the UK. We should agree a national protocol, based on CTAE version 3.0, and the data should be analysed automatically in real time to look for departures from the normal patterns of expected toxicities. The evaluation of the cost-effectiveness of this approach could be incorporated into the formal evaluation of IVD as outlined above.
   
5. We should not adopt any new intervention, in particular IVD, without ensuring that adequate resources — both people and money — are put in place beforehand.
   

The Chief Medical Officer's report presents us with a welcome challenge. We should rise to it.

	Footnotes

 
*James Carville was a political advisor to Bill Clinton during his 1992 election campaign. Carville had the following sign hung up in the campaign headquarters in Little Rock, Arkansas, its purpose being to serve as a prompt for staff who were dealing with questions and queries: "1. Change vs more of the same. 2. The economy, stupid. 3. Don't forget health care".

Donald Rumsfeld: The 13th (1975–1977) and 21st (2001–2006) US Secretary of Defense. He made the quoted remarks at a Defense Department briefing on 12 February 2002

**The term "Wiki" is derived from the Hawaiian word meaning "quick" or "rapid".

Received for publication October 2, 2007. Revision received October 8, 2007. Accepted for publication October 10, 2007.

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Top Patient safety -- context... The taxonomy of medical... Risks have to be... Errors in radiotherapy: the... Radiotherapeutic errors in the... The role of in... Reducing known errors,... Conclusions References

 

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