Does prostate screening make sense for you?
By Dr. Steven Woloshin and Dr. Lisa M. Schwartz
05 oct 2008--For years, American men have gotten a clear message: worry about prostate cancer, and get tested. The media, celebrity and politician testimonials, national prostate cancer awareness week - even a US Postal Service stamp - provide constant reminders that men face a big risk and that prostate-specific antigen screening is the responsible thing to do.
The commonly cited statistics are stark: almost 220,000 American men were diagnosed with prostate cancer last year; it is the most common nonskin cancer and the second-biggest cancer killer among men in the United States.
The message has gotten through. Most American men over 50 undergo prostate cancer screening: in 2006, nearly two-thirds of men between 50 and 74, and three-quarters of men older than 75, were screened in the past two years. Specialists have estimated that more than 1 million men have been diagnosed with prostate cancer because of screening.
But now the United States Preventive Services Task Force, the preeminent body making recommendations on preventive medical services in this country, has told physicians not to screen men 75 and older, and said screening for younger men is a toss-up.
The reason: Prostate cancer screening is a tradeoff between an uncertain benefit and known harms.
We don't know whether PSA screening (a blood test for prostate cancer) saves lives since the gold standard, randomized trials, have not been completed. But we do know that screening causes harm, such as false alarms leading to unnecessary biopsies and, more importantly, unnecessary diagnoses: finding cancers that would never have caused symptoms or death if left undetected.
PSA screening results in a lot of unnecessary diagnoses. But since there is no way to know whether an individual man has been unnecessarily diagnosed, most men with screen-detected prostate cancer get treated. That means there is a lot of unnecessary treatment (the cancers destined to never cause harm cannot be helped by - and do not need - treatment). Unfortunately, unnecessary treatment can cause harm, leaving a substantial proportion of men impotent or incontinent.
The task force concluded that for older men, harms outweigh benefits. They concluded that, for younger men, the balance of benefits and harms is too uncertain to justify recommending for or against screening. These men need to decide for themselves.
Shifting messages and limited evidence may leave men frustrated and confused. How can they decide what to do in the face of so much uncertainty?
The first step is to ask how big their risk of prostate cancer really is. If a man feels the risk is high, he might be willing to take the chance that screening does more good than harm; if he feels his risk is low, he may opt to forgo screening.
How can he judge this risk? Intuition tells him the risk must be big, given the commonly reported statistic: "220,000 cases diagnosed last year." But this statistic is deceptive because screening itself inflates the number of cases because of unnecessary diagnosis.
The result, ironically, is a self-reinforcing cycle: an inflated sense of risk leads more men to get screened; as more cases are detected, the risk looks bigger.
A better gauge of the true threat from prostate cancer is the chance of dying from it. But the most familiar statistic - 28,000 prostate cancer deaths last year - hides critical detail: the risk of prostate cancer death changes dramatically with age. That number also lacks perspective: other causes of death rise even faster with age. Without age-specific statistics and perspective, many men are probably left with an exaggerated sense of risk.
Our research shows that for younger men, there isn't much prostate risk to reduce. For the average 50-year-old, the chance of dying of prostate cancer in the next 10 years is 1 out of 1,000. Another way to say this is that, over the next 10 years, 999 out of 1,000 will not die from prostate cancer. For perspective, the risk of dying in an accident over this time is five times greater.
Risk increases with age, but does not reach 10 out of 1,000 until age 70. Some may feel that this amount of risk is insufficient to justify the potential harms of screening; others may feel that the risk is big enough. Men need to decide for themselves.
The risk to older men is indeed greater; by age 75, the 10-year risk of prostate cancer death approaches 20 in 1,000. But again, this number should be put in perspective. For men who never smoked, the chance of heart attack death is seven times greater than the chance of prostate cancer death. For current smokers, the chance of dying from either a heart attack, lung disease, or lung cancer is 20 times greater than that of prostate cancer.
Our point is not to minimize the real suffering caused by prostate cancer. It can be a terrible, fatal disease. Rather, it is that prostate screening has been heavily marketed to the public for years in ways that have exaggerated the risk of cancer and the benefit and safety of screening.
To really help men, we need to help them understand the risks they face and which ones can be reduced with interventions of proven benefit.
The authors are general internists at the Department of Veterans Affairs Medical Center in White River Junction, Vt., associate professors at the Dartmouth Institute for Health Policy & Clinical Practice in Hanover, N.H. , and the authors of Know Your Chances; Understanding Health Statistics.
The commonly cited statistics are stark: almost 220,000 American men were diagnosed with prostate cancer last year; it is the most common nonskin cancer and the second-biggest cancer killer among men in the United States.
The message has gotten through. Most American men over 50 undergo prostate cancer screening: in 2006, nearly two-thirds of men between 50 and 74, and three-quarters of men older than 75, were screened in the past two years. Specialists have estimated that more than 1 million men have been diagnosed with prostate cancer because of screening.
But now the United States Preventive Services Task Force, the preeminent body making recommendations on preventive medical services in this country, has told physicians not to screen men 75 and older, and said screening for younger men is a toss-up.
The reason: Prostate cancer screening is a tradeoff between an uncertain benefit and known harms.
We don't know whether PSA screening (a blood test for prostate cancer) saves lives since the gold standard, randomized trials, have not been completed. But we do know that screening causes harm, such as false alarms leading to unnecessary biopsies and, more importantly, unnecessary diagnoses: finding cancers that would never have caused symptoms or death if left undetected.
PSA screening results in a lot of unnecessary diagnoses. But since there is no way to know whether an individual man has been unnecessarily diagnosed, most men with screen-detected prostate cancer get treated. That means there is a lot of unnecessary treatment (the cancers destined to never cause harm cannot be helped by - and do not need - treatment). Unfortunately, unnecessary treatment can cause harm, leaving a substantial proportion of men impotent or incontinent.
The task force concluded that for older men, harms outweigh benefits. They concluded that, for younger men, the balance of benefits and harms is too uncertain to justify recommending for or against screening. These men need to decide for themselves.
Shifting messages and limited evidence may leave men frustrated and confused. How can they decide what to do in the face of so much uncertainty?
The first step is to ask how big their risk of prostate cancer really is. If a man feels the risk is high, he might be willing to take the chance that screening does more good than harm; if he feels his risk is low, he may opt to forgo screening.
How can he judge this risk? Intuition tells him the risk must be big, given the commonly reported statistic: "220,000 cases diagnosed last year." But this statistic is deceptive because screening itself inflates the number of cases because of unnecessary diagnosis.
The result, ironically, is a self-reinforcing cycle: an inflated sense of risk leads more men to get screened; as more cases are detected, the risk looks bigger.
A better gauge of the true threat from prostate cancer is the chance of dying from it. But the most familiar statistic - 28,000 prostate cancer deaths last year - hides critical detail: the risk of prostate cancer death changes dramatically with age. That number also lacks perspective: other causes of death rise even faster with age. Without age-specific statistics and perspective, many men are probably left with an exaggerated sense of risk.
Our research shows that for younger men, there isn't much prostate risk to reduce. For the average 50-year-old, the chance of dying of prostate cancer in the next 10 years is 1 out of 1,000. Another way to say this is that, over the next 10 years, 999 out of 1,000 will not die from prostate cancer. For perspective, the risk of dying in an accident over this time is five times greater.
Risk increases with age, but does not reach 10 out of 1,000 until age 70. Some may feel that this amount of risk is insufficient to justify the potential harms of screening; others may feel that the risk is big enough. Men need to decide for themselves.
The risk to older men is indeed greater; by age 75, the 10-year risk of prostate cancer death approaches 20 in 1,000. But again, this number should be put in perspective. For men who never smoked, the chance of heart attack death is seven times greater than the chance of prostate cancer death. For current smokers, the chance of dying from either a heart attack, lung disease, or lung cancer is 20 times greater than that of prostate cancer.
Our point is not to minimize the real suffering caused by prostate cancer. It can be a terrible, fatal disease. Rather, it is that prostate screening has been heavily marketed to the public for years in ways that have exaggerated the risk of cancer and the benefit and safety of screening.
To really help men, we need to help them understand the risks they face and which ones can be reduced with interventions of proven benefit.
The authors are general internists at the Department of Veterans Affairs Medical Center in White River Junction, Vt., associate professors at the Dartmouth Institute for Health Policy & Clinical Practice in Hanover, N.H. , and the authors of Know Your Chances; Understanding Health Statistics.
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