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How should doctors, and patients, think and talk about risk?
Urologic Oncology: Seminars and Original Investigations 26 (2008) 662– 664
Seminar section introduction
How should doctors, and patients, think and talk about risk? The articles in this issue are about a situation everyone dreads: that moment when we realize that our lives are in danger from disease, and that decisions on treatment must be made. In such moments we are not only face to face with our own mortality, but also with a difficult intellectual problem, for the future course of an illness, as well as the treatment options offered by the medical community, are probably not sure things. They have a variety of possible outcomes, with probabilities attached to each; in other words, they carry risk. And so, at our most vulnerable and frightened moment, we are turned in spite of ourselves into gamblers, playing for the highest stakes of all. The articles that follow all discuss the assessment of treatment risks and how doctors and patients should mutually deal with risky decision making. Risk is an interdisciplinary phenomenon. It is of primary concern for professionals as diverse as fighter pilots and insurance executives, stock brokers and politicians. In the academic world it is studied by professors of business, psychology, economics, international affairs, and mathematics, to name a few. So for this issue a political scientist, two economists and a clinical psychologist were invited to share their thoughts about how doctors and patients can best assess and discuss risk when they face daunting treatment decisions. The idea was to see whether those dealing with and studying risk outside the medical profession have insights to offer that can help when issues of mortality and treatment are at stake. This introductory article will attempt to set the scene for and guide the reader to their contributions.
What is risk? As Rose McDermott notes in her very first paragraph, risk is a mélange of two ingredients: chance and loss.1 Each applies to what may happen in the future, raising the possibility that one may be worse off than at present.2 Risk, of course, is never retrospective, for in the past there are no probabilities, only realities. 1
“Risk is brewed from an equal dose of two ingredients–probabilities and consequences” [1]. 2 Webster’s New International Dictionary of the English Language defines risk as the possibility of loss, injury, disadvantage or destruction. 1078-1439/08/$ – see front matter © 2008 Published by Elsevier Inc. doi:10.1016/j.urolonc.2007.12.008
Although computer geeks define risk as a threat exploiting a vulnerability, it is probably clearer to use “passive risk” or “danger” to denote a risk that comes at one from outside, as it were, separately from what one may intend doing. This approach would term the possibility of morbidity or death from disease a danger, however much it may have been caused by the patient’s prior behavior. The term “risk” would be reserved for the consequences of action taken to deal with the dangers disease poses. Active risks, those incurred by various treatment options, can be defined as the possibility (chance) that outcomes will differ from expectations in a negative way (loss). The chance part of risk is expressed as a probability, usually of less than 50%; indeed, risk is often defined as a loss that is less than 50% likely, or simply as a cost that one does not expect to pay (as contrasted with a cost one expects to pay).3 But it may also refer to a benefit less than 50% likely to be obtained, an objective one has a slim chance of achieving. Doctors’ responsibilities for the chance part of risk are to translate scientific data across prior patient outcomes into probabilities that apply to the patient’s particular situation, in terms the patient can understand. In doing so, they will often have to make clear that the probabilities associated with risk are not the same as uncertainty; probabilities are known, or at least can be estimated, whereas uncertainty refers to likelihoods of occurrence that are unknown (as well as to magnitudes of loss that are obscure).4 Like probability, the possible loss involved in taking risk may appear on either the cost or benefit side of the action; that is, one may pay unexpected costs or fail to achieve intended gains. Specifying loss has two aspects. One is establishing its magnitude, getting a sense of what might happen, of how severe the consequences of treatment or disease might be in terms of function or life expectancy. The other aspect is ascertaining the seriousness or value to the patient of those magnitudes. If probabilities are the objective result of scientific data, and magnitude can be understood through the physician’s descriptive power, valuation 3 From Ambassador Robert Gallucci, speech to National War College Class of 2000, August 31, 1999 (used by permission). 4 ‘“Risk-taking’ refers to . . . probability . . . ‘Uncertainty,’ on the other hand, refers to the degree to which the probability . . . is unknown” [2]. (See also Levy [3].)
T.L. Deibel / Urologic Oncology: Seminars and Original Investigations 26 (2008) 662– 664
must be done by patients themselves. These are the preferences discussed by Ben Sommers and Richard Zeckhauser, and while physicians must describe consequences completely and can help patients reason through their values, doctors must be wary of substituting their own values for those of their patients. No one but the patient knows, for example, whether coping with a neobladder or wearing a pouching system is the greater cost, or even whether a severely impaired life is better than death. And of course, as Mike Beasley makes powerfully clear, patients themselves may have a very hard time knowing, which is why uncertainty applies to evaluating the loss part of risk as well as to understanding the chance part. Moreover, as Beasley, Sommers, and Zeckhauser all attest, the anxiety caused by uncertainty can produce at least as much stress as certain but bad news.
Trading cost and risk Given that risk is all about loss, albeit improbable loss, why do people take it? In the situations these articles address, they do so because of the dangers posed by the diseases they face. That is, they do so because they have come to the conclusion, based both on the probabilities they understand and the values they assign, that they will likely be better off risking the treatments offered than risking the progression of the disease they have. To be sure, this calculation involves cost as well as risk: the expected losses involved not only in enduring the treatment, surgical or otherwise, but also of living with a missing breast or bladder. They are willing to pay those costs up front to reduce the much bigger, more highly-valued losses, probable and improbable, of doing nothing. As Zechhauser and Sommers point out, avoiding risk is itself a value to some patients. Like those who buy insurance, such patients are to some extent trading cost against danger, paying some amount now to reduce the chance that they will have to pay much more (or pay in a more highly-valued currency) later. They do so in spite of their uncertainties both about probabilities and about how things will really be, how they will really feel, when the consequences of treatment come to pass. It is worth pointing out that people take risk even when they are not confronted by danger, simply as the unavoidable concomitant of gain. They invest in the stock market in order to become wealthy, they speed in their cars to get somewhere sooner, they get married to enhance their personal happiness, they change jobs and locations to pursue career opportunities. The objectives of these actions are hardly sure things, and the potential costs (of financial ruin, injury or death, divorce, or unemployment) are obvious. But people take these risks anyway, in some cases because there is no other way to achieve the gain, in others because they do not have, or do not wish to use, the resources that would be needed to seek their objectives in a more certain, less risky way. In this sense, risk can also be seen as a gap between ends and means, between objectives and the resources necessary
663
to achieve them. Considered in isolation, the way the Iraq war was begun in 2003 is a good example; costs were kept low by employing a fraction of the troops used in the 1991 war, taking the risk that the country could not be controlled once Saddam Hussein’s regime was toppled.5 But whatever the situation, this kind of risk may be seen as positive, a way of getting something done at less cost or of expanding one’s objectives despite limited resources. Some elective surgery, such as having one’s stomach stapled to treat obesity, may be an example of taking the risks of surgery to avoid the costs associated with uncontrolled obesity (a case in which the losses attendant upon the procedure and its aftermath may have probabilities well below 50% and therefore be properly judged risks, while the losses of untreated weight gain may be well above 50% likely and therefore lie in the domain of cost). An opposite example would be the patient with bladder cancer who elects an early cystectomy, trading the substantial cost of surgery and its long-term consequences (including improbable or risky costs) against the relatively slight risk of contracting metastatic bladder cancer. Such a patient takes this lesser gamble because he knows that good odds in the larger one mean nothing if he comes up on the short end of the statistic, and that the loss if that happens can be catastrophic.
Taking risky decisions But many patients are not so fortunate. In many cases, a return to perfect health is not in the cards. They must pick the least bad alternative by comparing the likelihood and their valuation of the magnitude of loss that untreated disease could bring, with the probabilities and their valuation of the costs and benefits that various treatment options hold. In doing so they must also assess the possible complications that come even with successful surgery, not only to assign value to the losses those complications represent, but also to consider the costs and risks of interventions to deal with them. For example, a 50-year-old male patient who faces a cystectomy has a better than 40% chance of erectile dysfunction, with the probability increasing about 10% with every decade of age [5]. He must first consider how important that loss would be for him if it occurred, along a scale that runs from raising serious issues of masculine identity at one end to being quite content with bringing that aspect of his life to a permanent close at the other. But if he concludes that continuing sexual function is important, he must also weigh the costs and risk of taking Viagra or Cialis, of injection therapy, or of penile implants to correct it, along with the costs and risk of interventions that might be needed to deal with the complications of those interventions. Given that there may be a half-dozen such complications that
5
For an elaboration of this point, as well as of the broader issue of trading costs and risks, see Deibel [4].
664
T.L. Deibel / Urologic Oncology: Seminars and Original Investigations 26 (2008) 662– 664
attend various treatment options, all of which require similar evaluation, the result could be a rather elaborate, multi-level analysis that would tax the patience and intelligence of even a healthy individual. There are other features of risk assessment to which patients and their doctors should be alert. One is that probability estimates are of necessity based on the experience of groups of patients, so depending on how broadly the group is defined, a given patient’s personal risk profile may differ substantially from the available statistics. Along with taking care to provide final and absolute risk statistics, as Zeckhauser and Sommers recommend, doctors can help patients locate the precise circumstances of their case along the spectrum of disease represented by the statistical group. Another is that statistics are usually given separately for each postsurgical complication rather than for all of them together, but the probabilities of those complications are partially additive. For example, cystectomy may be followed by chronic urinary tract infections, intestinal blockages, kidney stone formation leading to deterioration of renal function, metabolic imbalances, hernia formation near the stoma, or scarring that blocks the flow of urine at one or another point in the reconstruction, to name six [5]. If we say for purposes of illustration that each of these has a roughly 10% probability, a patient surveying the list could be led to see it as 90% probable that she’ll escape them all.6 In fact, she has only a 53% chance of experiencing no complications and about a 35% chance of getting at least one (if only a 10% chance of getting any two and a 1.50% chance of getting three).7 Such intellectual traps merely add to the psychological pitfalls, so interestingly discussed by Rose McDermott, which doctors can help patients avoid. How then should patients and doctors assess the risk of various treatments? A rough approach to the task, gleaned from the articles that follow, might look something like this: ● As a baseline, assess the likely courses of the disease and their probabilities; assign value to those eventualities; and explore later treatments for each, with their costs, risks, and probabilities of success. (Doctor and Patient) ● Define treatment options. (Doctor) ● Ascertain the probability of success for each, and define its benefit. (Doctor) ● Specify the expected loss (costs) resulting from each, the likelihood of unexpected loss (risks), and the na6 The 10% figures are most accurate for kidney stones, metabolic imbalances, infection, and bowel obstruction; the probability of scar formation may be as high as 20%, and the possibility of hernia development varies with the physical condition of the abdominal muscle and fascia at the time of surgery. 7 The reason the probability of getting a complication is not 60% is that each of the six situations in which the patient gets only one includes a 90% probability that she not have each of the other five. (I am indebted to Catherine M. Deibel for the probability calculations displayed here.)
●
● ● ● ●
ture and magnitude of those costs and risks, using final (rather than intermediate) and absolute (rather than relative) probabilities, and being aware of the relationship of the patient’s individual case to the group on which probability statistics are based. (Doctor) Be alert to the psychological effects of the availability heuristic, to where one is placing the reference point between loss and gain, to the tendency to see highly improbable or probable outcomes as impossible or certain, and to the utility of accepting some risk in the pursuit of highly valued gain. (Patient) Assign values to each set of costs and risks, and to each successful outcome, being careful to frame each in both positive and negative terms. (Patient) Elaborate the costs and risks of dealing with those losses, and of treatment options for those risks should they materialize. (Doctor) Compare benefits, costs, and risks of each treatment option with the likely consequences of watchful waiting. (Doctor and Patient) Factor in personal tolerances for anxiety and risk, and preferences for the short vs. the long term. (Patient)
Such an elaborate, if informal, procedure may seem like a counsel of perfection to people caught up in the kind of trauma Mike Beasley describes, people who feel they are suddenly in a parallel universe, awake during their own nightmares. Such patients pray for strength and courage in their ordeals, wisdom to make the right decisions regarding treatment, and hope for the future. Though little can be immediately done to relieve their anguish, following the kind of systematic approach to decision-making sketched above may help support their confidence in treatment decisions and thereby contribute to the strength, courage, and hope they need at a most difficult time of life. Terry L. Deibel, Ph.D. Professor of National Strategy National War College National Defense University Washington, D.C., USA References [1] Slovic P. Informing and educating the public about risk. Risk Anal 1986;6:412. [2] Bueno de Mesquita B. The war trap. New Haven (CT): Yale University Press, 1981. p. 33. [3] Levy JS. An introduction to prospect theory, and prospect theory and international relations: Theoretical applications and analytical problems. In: Farnham B, editor. Avoiding losses/taking risks: Prospect theory and international conflict. Ann Arbor (MI): University of Michigan Press, 1994. p. 8. 9, 129. [4] Deibel TL. Foreign affairs strategy: Logic for American statecraft. New York: Cambridge University Press, 2007. p. 340 –53. [5] Schoenberg MP. The guide to living with bladder cancer. Baltimore (MD): Johns Hopkins University Press, 2000. p. 78, 85.
Seminar section introduction
How should doctors, and patients, think and talk about risk? The articles in this issue are about a situation everyone dreads: that moment when we realize that our lives are in danger from disease, and that decisions on treatment must be made. In such moments we are not only face to face with our own mortality, but also with a difficult intellectual problem, for the future course of an illness, as well as the treatment options offered by the medical community, are probably not sure things. They have a variety of possible outcomes, with probabilities attached to each; in other words, they carry risk. And so, at our most vulnerable and frightened moment, we are turned in spite of ourselves into gamblers, playing for the highest stakes of all. The articles that follow all discuss the assessment of treatment risks and how doctors and patients should mutually deal with risky decision making. Risk is an interdisciplinary phenomenon. It is of primary concern for professionals as diverse as fighter pilots and insurance executives, stock brokers and politicians. In the academic world it is studied by professors of business, psychology, economics, international affairs, and mathematics, to name a few. So for this issue a political scientist, two economists and a clinical psychologist were invited to share their thoughts about how doctors and patients can best assess and discuss risk when they face daunting treatment decisions. The idea was to see whether those dealing with and studying risk outside the medical profession have insights to offer that can help when issues of mortality and treatment are at stake. This introductory article will attempt to set the scene for and guide the reader to their contributions.
What is risk? As Rose McDermott notes in her very first paragraph, risk is a mélange of two ingredients: chance and loss.1 Each applies to what may happen in the future, raising the possibility that one may be worse off than at present.2 Risk, of course, is never retrospective, for in the past there are no probabilities, only realities. 1
“Risk is brewed from an equal dose of two ingredients–probabilities and consequences” [1]. 2 Webster’s New International Dictionary of the English Language defines risk as the possibility of loss, injury, disadvantage or destruction. 1078-1439/08/$ – see front matter © 2008 Published by Elsevier Inc. doi:10.1016/j.urolonc.2007.12.008
Although computer geeks define risk as a threat exploiting a vulnerability, it is probably clearer to use “passive risk” or “danger” to denote a risk that comes at one from outside, as it were, separately from what one may intend doing. This approach would term the possibility of morbidity or death from disease a danger, however much it may have been caused by the patient’s prior behavior. The term “risk” would be reserved for the consequences of action taken to deal with the dangers disease poses. Active risks, those incurred by various treatment options, can be defined as the possibility (chance) that outcomes will differ from expectations in a negative way (loss). The chance part of risk is expressed as a probability, usually of less than 50%; indeed, risk is often defined as a loss that is less than 50% likely, or simply as a cost that one does not expect to pay (as contrasted with a cost one expects to pay).3 But it may also refer to a benefit less than 50% likely to be obtained, an objective one has a slim chance of achieving. Doctors’ responsibilities for the chance part of risk are to translate scientific data across prior patient outcomes into probabilities that apply to the patient’s particular situation, in terms the patient can understand. In doing so, they will often have to make clear that the probabilities associated with risk are not the same as uncertainty; probabilities are known, or at least can be estimated, whereas uncertainty refers to likelihoods of occurrence that are unknown (as well as to magnitudes of loss that are obscure).4 Like probability, the possible loss involved in taking risk may appear on either the cost or benefit side of the action; that is, one may pay unexpected costs or fail to achieve intended gains. Specifying loss has two aspects. One is establishing its magnitude, getting a sense of what might happen, of how severe the consequences of treatment or disease might be in terms of function or life expectancy. The other aspect is ascertaining the seriousness or value to the patient of those magnitudes. If probabilities are the objective result of scientific data, and magnitude can be understood through the physician’s descriptive power, valuation 3 From Ambassador Robert Gallucci, speech to National War College Class of 2000, August 31, 1999 (used by permission). 4 ‘“Risk-taking’ refers to . . . probability . . . ‘Uncertainty,’ on the other hand, refers to the degree to which the probability . . . is unknown” [2]. (See also Levy [3].)
T.L. Deibel / Urologic Oncology: Seminars and Original Investigations 26 (2008) 662– 664
must be done by patients themselves. These are the preferences discussed by Ben Sommers and Richard Zeckhauser, and while physicians must describe consequences completely and can help patients reason through their values, doctors must be wary of substituting their own values for those of their patients. No one but the patient knows, for example, whether coping with a neobladder or wearing a pouching system is the greater cost, or even whether a severely impaired life is better than death. And of course, as Mike Beasley makes powerfully clear, patients themselves may have a very hard time knowing, which is why uncertainty applies to evaluating the loss part of risk as well as to understanding the chance part. Moreover, as Beasley, Sommers, and Zeckhauser all attest, the anxiety caused by uncertainty can produce at least as much stress as certain but bad news.
Trading cost and risk Given that risk is all about loss, albeit improbable loss, why do people take it? In the situations these articles address, they do so because of the dangers posed by the diseases they face. That is, they do so because they have come to the conclusion, based both on the probabilities they understand and the values they assign, that they will likely be better off risking the treatments offered than risking the progression of the disease they have. To be sure, this calculation involves cost as well as risk: the expected losses involved not only in enduring the treatment, surgical or otherwise, but also of living with a missing breast or bladder. They are willing to pay those costs up front to reduce the much bigger, more highly-valued losses, probable and improbable, of doing nothing. As Zechhauser and Sommers point out, avoiding risk is itself a value to some patients. Like those who buy insurance, such patients are to some extent trading cost against danger, paying some amount now to reduce the chance that they will have to pay much more (or pay in a more highly-valued currency) later. They do so in spite of their uncertainties both about probabilities and about how things will really be, how they will really feel, when the consequences of treatment come to pass. It is worth pointing out that people take risk even when they are not confronted by danger, simply as the unavoidable concomitant of gain. They invest in the stock market in order to become wealthy, they speed in their cars to get somewhere sooner, they get married to enhance their personal happiness, they change jobs and locations to pursue career opportunities. The objectives of these actions are hardly sure things, and the potential costs (of financial ruin, injury or death, divorce, or unemployment) are obvious. But people take these risks anyway, in some cases because there is no other way to achieve the gain, in others because they do not have, or do not wish to use, the resources that would be needed to seek their objectives in a more certain, less risky way. In this sense, risk can also be seen as a gap between ends and means, between objectives and the resources necessary
663
to achieve them. Considered in isolation, the way the Iraq war was begun in 2003 is a good example; costs were kept low by employing a fraction of the troops used in the 1991 war, taking the risk that the country could not be controlled once Saddam Hussein’s regime was toppled.5 But whatever the situation, this kind of risk may be seen as positive, a way of getting something done at less cost or of expanding one’s objectives despite limited resources. Some elective surgery, such as having one’s stomach stapled to treat obesity, may be an example of taking the risks of surgery to avoid the costs associated with uncontrolled obesity (a case in which the losses attendant upon the procedure and its aftermath may have probabilities well below 50% and therefore be properly judged risks, while the losses of untreated weight gain may be well above 50% likely and therefore lie in the domain of cost). An opposite example would be the patient with bladder cancer who elects an early cystectomy, trading the substantial cost of surgery and its long-term consequences (including improbable or risky costs) against the relatively slight risk of contracting metastatic bladder cancer. Such a patient takes this lesser gamble because he knows that good odds in the larger one mean nothing if he comes up on the short end of the statistic, and that the loss if that happens can be catastrophic.
Taking risky decisions But many patients are not so fortunate. In many cases, a return to perfect health is not in the cards. They must pick the least bad alternative by comparing the likelihood and their valuation of the magnitude of loss that untreated disease could bring, with the probabilities and their valuation of the costs and benefits that various treatment options hold. In doing so they must also assess the possible complications that come even with successful surgery, not only to assign value to the losses those complications represent, but also to consider the costs and risks of interventions to deal with them. For example, a 50-year-old male patient who faces a cystectomy has a better than 40% chance of erectile dysfunction, with the probability increasing about 10% with every decade of age [5]. He must first consider how important that loss would be for him if it occurred, along a scale that runs from raising serious issues of masculine identity at one end to being quite content with bringing that aspect of his life to a permanent close at the other. But if he concludes that continuing sexual function is important, he must also weigh the costs and risk of taking Viagra or Cialis, of injection therapy, or of penile implants to correct it, along with the costs and risk of interventions that might be needed to deal with the complications of those interventions. Given that there may be a half-dozen such complications that
5
For an elaboration of this point, as well as of the broader issue of trading costs and risks, see Deibel [4].
664
T.L. Deibel / Urologic Oncology: Seminars and Original Investigations 26 (2008) 662– 664
attend various treatment options, all of which require similar evaluation, the result could be a rather elaborate, multi-level analysis that would tax the patience and intelligence of even a healthy individual. There are other features of risk assessment to which patients and their doctors should be alert. One is that probability estimates are of necessity based on the experience of groups of patients, so depending on how broadly the group is defined, a given patient’s personal risk profile may differ substantially from the available statistics. Along with taking care to provide final and absolute risk statistics, as Zeckhauser and Sommers recommend, doctors can help patients locate the precise circumstances of their case along the spectrum of disease represented by the statistical group. Another is that statistics are usually given separately for each postsurgical complication rather than for all of them together, but the probabilities of those complications are partially additive. For example, cystectomy may be followed by chronic urinary tract infections, intestinal blockages, kidney stone formation leading to deterioration of renal function, metabolic imbalances, hernia formation near the stoma, or scarring that blocks the flow of urine at one or another point in the reconstruction, to name six [5]. If we say for purposes of illustration that each of these has a roughly 10% probability, a patient surveying the list could be led to see it as 90% probable that she’ll escape them all.6 In fact, she has only a 53% chance of experiencing no complications and about a 35% chance of getting at least one (if only a 10% chance of getting any two and a 1.50% chance of getting three).7 Such intellectual traps merely add to the psychological pitfalls, so interestingly discussed by Rose McDermott, which doctors can help patients avoid. How then should patients and doctors assess the risk of various treatments? A rough approach to the task, gleaned from the articles that follow, might look something like this: ● As a baseline, assess the likely courses of the disease and their probabilities; assign value to those eventualities; and explore later treatments for each, with their costs, risks, and probabilities of success. (Doctor and Patient) ● Define treatment options. (Doctor) ● Ascertain the probability of success for each, and define its benefit. (Doctor) ● Specify the expected loss (costs) resulting from each, the likelihood of unexpected loss (risks), and the na6 The 10% figures are most accurate for kidney stones, metabolic imbalances, infection, and bowel obstruction; the probability of scar formation may be as high as 20%, and the possibility of hernia development varies with the physical condition of the abdominal muscle and fascia at the time of surgery. 7 The reason the probability of getting a complication is not 60% is that each of the six situations in which the patient gets only one includes a 90% probability that she not have each of the other five. (I am indebted to Catherine M. Deibel for the probability calculations displayed here.)
●
● ● ● ●
ture and magnitude of those costs and risks, using final (rather than intermediate) and absolute (rather than relative) probabilities, and being aware of the relationship of the patient’s individual case to the group on which probability statistics are based. (Doctor) Be alert to the psychological effects of the availability heuristic, to where one is placing the reference point between loss and gain, to the tendency to see highly improbable or probable outcomes as impossible or certain, and to the utility of accepting some risk in the pursuit of highly valued gain. (Patient) Assign values to each set of costs and risks, and to each successful outcome, being careful to frame each in both positive and negative terms. (Patient) Elaborate the costs and risks of dealing with those losses, and of treatment options for those risks should they materialize. (Doctor) Compare benefits, costs, and risks of each treatment option with the likely consequences of watchful waiting. (Doctor and Patient) Factor in personal tolerances for anxiety and risk, and preferences for the short vs. the long term. (Patient)
Such an elaborate, if informal, procedure may seem like a counsel of perfection to people caught up in the kind of trauma Mike Beasley describes, people who feel they are suddenly in a parallel universe, awake during their own nightmares. Such patients pray for strength and courage in their ordeals, wisdom to make the right decisions regarding treatment, and hope for the future. Though little can be immediately done to relieve their anguish, following the kind of systematic approach to decision-making sketched above may help support their confidence in treatment decisions and thereby contribute to the strength, courage, and hope they need at a most difficult time of life. Terry L. Deibel, Ph.D. Professor of National Strategy National War College National Defense University Washington, D.C., USA References [1] Slovic P. Informing and educating the public about risk. Risk Anal 1986;6:412. [2] Bueno de Mesquita B. The war trap. New Haven (CT): Yale University Press, 1981. p. 33. [3] Levy JS. An introduction to prospect theory, and prospect theory and international relations: Theoretical applications and analytical problems. In: Farnham B, editor. Avoiding losses/taking risks: Prospect theory and international conflict. Ann Arbor (MI): University of Michigan Press, 1994. p. 8. 9, 129. [4] Deibel TL. Foreign affairs strategy: Logic for American statecraft. New York: Cambridge University Press, 2007. p. 340 –53. [5] Schoenberg MP. The guide to living with bladder cancer. Baltimore (MD): Johns Hopkins University Press, 2000. p. 78, 85.