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Cancer, Heart Disease, New Study
This week the American Cancer Society published its annual review of cancer statistics and trends. This year the big picture was overwhelmingly positive.
The three most frequently diagnosed cancers in men are prostate cancer, lung cancer, and colorectal cancer (in that order). For women the top three are breast, lung and colorectal cancer. (See the link below to Figure 1 in the study for details.) The incidences (the numbers of new diagnoses every year) of all of these cancers have decreased in the last few years, except for lung cancer in women, which is still increasing but at a slower rate than previously.
The continued decline in lung cancer in men is attributed to the decrease in smoking in men in the last few decades. Women, on the other hand, started smoking in significant numbers later than men in the twentieth century, but also continued to smoke after men were quitting. The peak of number of women smokers was 20 years after the peak for men, so the decline in lung cancer in women hasn’t happened yet (but will).
Colon cancer incidence continues to fall in both men and women, likely because of increased colon cancer screening with colonoscopy, leading to the removal of pre-malignant polyps.
In terms of deaths caused by cancer, the top four causes for men are (in order) lung, prostate, colorectal and pancreas. For women the top four are lung, breast, colorectal and pancreas. Note that prostate cancer and breast cancer are the most common causes of cancer in men and women, but since they are very treatable and sometimes even curable, they are only the second most common causes of cancer death. The opposite case is pancreatic cancer. It is the tenth most common cause of cancer, but because it is so frequently fatal, it is the fourth most common cause of cancer death.
Fortunately, the mortality rates from lung, breast, prostate and colorectal cancer are all falling, likely due to improvements in diagnosis and treatment. So over all, fewer Americans are dying of cancer due largely to advances in the treatments for these top four killers. Interestingly, mortality from pancreatic cancer has not changed dramatically, making me wonder whether it will overtake colon cancer as the trends continue.
During the same years in which these positive trends were occurring in cancer, major advances were also being made in heart disease. Because of improved treatments for blood pressure and cholesterol, and because fewer Americans are smoking, the mortality from heart disease has been falling for many years. Heart disease is still the most common cause of death in the US, with cancer a close second. Because of the drop in heart disease mortality, cancer is now the leading cause of death for those 85 and younger. (See the link below to Figure 6 for details.)
That’s all very encouraging news, except that it probably means that our children will all die of pancreatic cancer or Alzheimer’s disease. Perhaps our grandchildren will return to smoking…
Learn more:
American Cancer Society article: Cancer Statistics, 2010
Figure 1: Ten Leading Cancer Types for the Estimated New Cancer Cases and Deaths by Sex, 2010.
Reuters article: U.S. cancer death rates continue drop: report
My regular readers know that prostate cancer screening has been an active research topic recently. (My not-so-regular readers who are interested are invited to catch up on the topic by reading my most recent post on the subject. See the link below.) Whether testing men for prostate cancer saves lives is still an open question. Large trials are currently underway that should provide a definitive answer in the next few years.
In the meantime, preliminary results from a Swedish trial give prostate screening a boost. The study, published in The Lancet, randomized 20,000 men between 50 and 64 years of age to a group that was invited to undergo PSA testing every 2 years, and another group that was not. The men in the screening group were offered PSA tests until they reached age 70. Men with elevated PSAs were offered further testing such as digital rectal examinations and prostate biopsies.
As expected, more prostate cancer was diagnosed in the screening group than in the control group. 12.7% of the men in the screening group were diagnosed with prostate cancer compared to 8.2% in the control group. Also as expected, the mortality rate from prostate cancer was quite low, as prostate cancer typically grows quite slowly and takes many years to cause harm. Nevertheless, the screening group showed a survival advantage. The risk of death from prostate cancer was 0.90% for the control group and only 0.50% in the screening group.
This means that (at least in this study) screening for prostate cancer saved lives. For each life saved, 293 men needed to be invited for screening and followed for an average of 14 years and 12 men were diagnosed with prostate cancer. Similar to mammography screening for breast cancer, the vast majority of people screened were not helped, and some were certainly harmed by surgery for cancer that would not have shortened their lives. Others died of prostate cancer despite being screened.
This is the first glimmer suggesting that routine PSAs may indeed be life-saving, with benefits in the same numerical ball-park as mammograms for breast cancer. Definitive answers are expected in the next few years as larger studies are completed.
Learn more:
The Lancet article: Mortality results from the Göteborg randomised population-based prostate-cancer screening trial
Wall Street Journal Health Blog post: Swedish Trial Finds Prostate-Cancer Screening Saves Lives
Reuters article: Study finds prostate screening cuts cancer deaths
My last post about prostate cancer screening: American Cancer Society Revises its Guidelines for Prostate Cancer Screening
My regular readers know the controversies and challenges posed by prostate cancer. It is very common. Over half the men who die at advanced age of other causes will have prostate cancer on autopsy. It is very slow. From the time that prostate cancer is detectable on biopsy to the time that it causes symptoms or shortens life can be as long as a decade. It is not very lethal. Because it tends to affect older men, most men diagnosed with it tend to die of other causes. Though it does kill tens of thousands of men annually, it kills fewer (and older) people than colon cancer, lung cancer or breast cancer (or traffic accidents).
This confluence of a very common but very indolent disease that strikes mostly older men has made screening, diagnosis and treatment very challenging. Should we be testing for a disease that lots of people will get but that most people won’t be harmed by? No one knows yet.
These challenges have prompted some researchers to consider prevention. What if instead of testing, diagnosing and treating we could give men at high risk of prostate cancer a medicine that made prostate cancer less likely? To be more cynical, the finances are also tempting since many more “at risk” men would have to take a preventive medicine than would actually get prostate cancer.
A large study published in this week’s New England Journal of Medicine shows that dutasteride, sold under the brand name Avodart, can decrease the incidence of prostate cancer in some men. This has received much media attention. (See links below.) But let’s review the details before prescribing it to your uncle and grandpa.
The study enrolled over 8,000 men who were thought to be at high risk for prostate cancer because of their age or an elevated PSA. (PSA is a not-very-accurate blood test used to test for prostate cancer.) They all had a prostate biopsy at the beginning of the study and only those with negative biopsies (i.e. no detectable cancer) were enrolled. Half the men were randomized to take Avodart daily, and half to placebo. All the men had prostate biopsies two years and four years after enrollment. The study sought to find if there was a difference in the numbers of prostate cancers found in the biopsies of the two groups.
Sure enough, Avodart seemed to decrease the incidence of prostate cancer found in the biopsies. 20% of the men taking Avodart were found to have prostate cancer versus 25% of the men taking placebo. But so what? Not a single person in either group died of prostate cancer, and they wouldn’t have been expected to since the study lasted four years and prostate cancer takes much longer than that to cause harm.
There’s absolutely no way to know if the men taking Avodart will live longer or be spared the symptoms of prostate cancer without following them for a much longer time. There is good reason to suspect that the men taking Avodart won’t do much better than the men taking placebo. The number of very aggressive tumors (as measured by their Gleason score, a quantitative score related to the tumors’ microscopic appearance) was the same in each group. It was only the least aggressive tumors that were decreased in the Avodart group.
Moreover, about 5% more men in the Avodart group than in the placebo group developed problems with libido or with erections. So for every 20 men who take Avodart rather than placebo for 4 years, one fewer man develops prostate cancer on biopsy which may or may not ever harm him, but one additional man develops sexual side effects. Add to that a small additional risk (about half a percent) of heart failure in the Avodart group, and the numbers are very discouraging.
An editorial in the same issue of the New England Journal of Medicine concludes that Avodart should not yet be prescribed for prostate cancer prevention. We need to know much more about the outcomes of men who take it for decades, not years.
Learn more:
New England Journal of Medicine article: Effect of Dutasteride on the Risk of Prostate Cancer
New England Journal of Medicine editorial: Chemoprevention of Prostate Cancer
Los Angeles Times article: Prostate drug may work as a preventive
Associated Press article: Study finds possible heart risk with prostate drug
About a year ago I reviewed the controversies of prostate cancer screening, especially the conundrum that we still don’t know whether finding prostate cancer early saves any lives. I concluded by citing the US Preventive Services Task Force (USPSTF) recommendations that the evidence is insufficient to recommend for or against screening for prostate cancer in men age 50 to 75. The USPSTF recommends against screening men older than 75 as the evidence suggests that harms outweigh benefits in these men.
What does screening for prostate cancer mean? There are two tests that are used to test for prostate cancer. One is a blood test called prostate specific antigen (PSA). The second is the not-always-popular digital rectal exam (DRE) in which a physician physically palpates the prostate in an attempt to feel an abnormality.
In contrast to the USPSTF, the American Cancer Society (ACS) has traditionally recommended more aggressive prostate cancer screening than was strictly supported by the evidence. This week, the ACS issued revised prostate cancer screening guidelines that better reflect the current uncertainties in the science. The new guidelines are much closer to the USPSTF recommendations.
The major changes in the new ACS guidelines are:
I understand that for many of my patients avoiding the DRE will be the highlight of their annual exam. But the bigger point that these guidelines struggle with is the fact that we have no idea whether or not we should be testing men for prostate cancer. Even worse, we are sure that some of the men who will be tested will be found to have prostate cancer and will be harmed by side effects of the subsequent treatment much more than their prostate cancer would have hurt them.
We will have better studies in the next few years that will attempt to answer if prostate cancer screening saves lives. In the meantime we have to make difficult decisions in the absence of adequate information.
Learn more:
American Cancer Society Revised Prostate Cancer Screening Guidelines: What Has–and Hasn’t—Changed
Los Angeles Times article: Education should accompany prostate screening, new guidelines say
Wall Street Journal Health Blog post: New Prostate Cancer Guidelines: Routine Screening Still Unneeded
My last post about prostate cancer screening: Screening for Prostate Cancer May Harm More than Help
This week the US Preventive Services Task Force (USPSTF) revised their recommendations for screening mammograms. Their recommendations have ignited much controversy and have weakened the credibility of a formerly objective scientific body.
This post is longer than usual. It deals with an important subject in some detail. For the readers who like to delve into the details and see the data, set this aside for when you can give it some time, follow the links, and check out the articles yourself. If you just want an executive summary, skim for the bold face type and read the conclusion.
What did the USPSTF recommend?
My regular readers know that the USPSTF is a national body of scientists who periodically assess the medical literature and provide recommendations about preventive tests and treatments. Because they are unaffiliated with any specific interest group, the USPSTF developed a reputation as the most objective and unbiased source of medical recommendations. For every test or therapy they reviewed, they weighed patient benefit against the potential for patient harm (regardless of cost) and reported whether the intervention was beneficial, harmful or that there is insufficient evidence to decide. I personally looked to their recommendations and wrote about them frequently.
The USPSTF’s last review of the literature regarding mammograms was in 2002. At that time they recommended a mammogram every one to two years for women aged 40 and older.
This week, in the Annals of Internal Medicine they published their new recommendations, supported by two articles detailing the scientific evidence that was reviewed to reach their conclusions. Their current recommendation (link 1 below) for mammograms is
The USPSTF recommends against routine screening mammography in women aged 40 to 49 years. The decision to start regular, biennial screening mammography before the age of 50 years should be an individual one and take into account patient context, including the patient’s values regarding specific benefits and harms.
The USPSTF recommends biennial screening mammography for women between the ages of 50 and 74 years.
The USPSTF concludes that the current evidence is insufficient to assess the additional benefits and harms of screening mammography in women 75 years or older.
So the major changes from 2002 are that
Shockingly, the first two points are entirely contradicted by the scientific evidence on which the recommendations are based.
What are the benefits and harms of mammograms for women in their 40s?
The article which examines the harms and benefits of mammograms in different age groups can be found at link 2, below. Table 1 (Pooled Risk Ratios for Breast Cancer Mortality From Mammography Screening Trials for All Ages) is a very helpful review of the pooled data from all the randomized trials for mammography in different age groups. The table shows how many women are needed to be invited to undergo mammograms in each age group to prevent 1 death from breast cancer. The numbers for women in their 60s are terrific. 377 women in their 60s need to be offered mammography to save 1 life from breast cancer. (The lower the number of women who must undergo mammograms to save one life, the more beneficial the intervention.) In their 50s 1,339 women must be screened to save a life, and in their 40s 1,904 must be screened. So mammography is still life-saving for women in their 40s it just saves fewer lives than for women in their 50s and 60s. In fact, the abstract of the article concludes
Mammography screening reduces breast cancer mortality for women aged 39 to 69 years.
So if mammograms have a life-saving benefit for women in their 40s, albeit a much smaller one than for women in their 50s or 60s, why would they not be recommended? Perhaps the harms caused by mammograms in that age group outweigh the benefits.
The article also methodically reviewed harms caused by mammograms. The risk posed by radiation exposure due to mammograms was studied without conclusive evidence of significant harm. The pain, anxiety and distress associated with undergoing mammograms and being told about potentially abnormal results were also studied. Most women surveyed reported that the pain and anxiety would not deter them from future mammograms. The most important harms that may result from mammography is a biopsy to determine if an abnormality is benign or malignant, additional imaging that may be required, and overdiagnosis, which means the diagnosis of breast cancer that is so slow-growing it is unlikely to shorten the woman’s lifespan.
Table 2 (Age-Specific Screening Results From the Breast Cancer Surveillance Consortium) summarizes the potential harms by age per 1,000 women screened. We would expect the harms in women in their 40s to outbalance the benefits and lead to the recommendation against mammograms at that age. The left column in the table deals with women in their 40s. Recall that it takes 1,904 women to be screened to save one life from breast cancer in that age group. Since the table shows the harms per 1,000 women screened, if we multiply each number by 1,904/1,000 we discover the harms that result from saving one life in this age group. So to save one life from breast cancer by screening women in their 40s with mammograms we would have to inflict 186 women with false positive mammogram results (abnormal mammograms without any cancer present), 161 women would have to undergo additional imaging and 18 women would have to undergo biopsies.
Now, I don’t want to minimize the misery involved in an unnecessary breast biopsy (unnecessary only in hindsight, of course). The procedure itself is uncomfortable and waiting for results is torture. Still, 18 biopsies to save one life strikes me as a wonderful trade-off, especially given that saving a life in the 40s yields many years of additional living. How can the USPSTF possibly judge that these harms outweigh the benefits? They hedge their recommendation by saying that the decision should be individualized for each patient, but that’s true for all medical decisions. Why then recommend against it?
Because it’s sometimes difficult to understand the numbers involved, I ask you to do the following thought experiment. You are a physician addressing an auditorium of 1,904 women in their 40s. You tell them “If you all have mammograms before you turn 50 one of your lives will be saved from breast cancer compared to just waiting until you all turn 50. Some of you will get breast cancer and die of it whether you get mammograms or not, and most of you won’t get breast cancer. If you start mammograms now, 18 of you will get biopsies, and a lot of you will get incorrect initial mammogram results requiring more mammograms or ultrasounds or MRIs. But only one of you will have her life saved from breast cancer.” Each woman can and should decide for herself but they’d like a recommendation from you.
I can’t imagine not recommending mammograms under this circumstance. Of course some women may choose against mammography, but to me the harms seem minor compared to the benefits.
How frequently should women have mammograms?
The decision to recommend biennial mammograms is based on a study published in an article at link 3, below. The study uses various models to compare the harms and benefits from different mammogram frequencies. But this article does something that has generally been outside the purview of the USPSTF. It considers cost.
The results state that having a mammogram every two years had 81% of the benefit of annual mammograms with far fewer false-positive results, unnecessary biopsies and additional imaging. And they state explicitly that annual mammograms consume more resources than mammograms every other year.
There are two important objections to this. First of all, getting only 81% of the life-saving benefits of annual mammograms may not strike many women as a victory. Why not capture all the benefits by having the test annually? The answer might be the additional harms, but as we’ve seen in the previous section, the harms are quite modest and most women would not be deterred by them. The second objection is that previously the unique value of the USPSTF was that it advised physicians about the value of tests regardless of costs. That allowed us to give patients the best advice we could, and allowed patients to decide if the cost was worth the benefit. Now, the USPSTF is deciding for us that annual mammograms are too expensive.
Conclusion
So, I and many other physicians will advise women to have annual mammograms starting at age 40. And in my opinion they should continue to do so until they are ill or frail enough that a new diagnosis of breast cancer would be unlikely to shorten their lives. For some women this might be in their 70s, for others, in their 80s.
But the broader outrage is that a group that I used to turn to without hesitation for objective review of the scientific data, a group that informed my daily advice to patients, has provided recommendations inconsistent with their own data and motivated by economics. Patients and physicians have neither the skills nor the time to scour the world literature on important topics. Who will fill the role that the USPSTF abandoned?
Learn more:
Scientific articles:
(1) Screening for Breast Cancer: U.S. Preventive Services Task Force Recommendation Statement
(2) Screening for Breast Cancer: An Update for the U.S. Preventive Services Task Force
Media coverage:
New York Times article: Panel Urges Mammograms at 50, Not 40
LA Times article: Mammogram guidelines spark heated debate
Wall Street Journal Editorial: A Breast Cancer Preview
Cancer, Infectious Diseases, New Study, Prevention
Last week I lamented that we can prevent so few cancers. Cervical cancer screening is one of the success stories of prevention. Regular pap smears can drastically decrease the risk of cervical cancer and makes death from cervical cancer virtually unheard of.
Cervical cancer is a sexually transmitted disease, caused by human pappilomavirus (HPV). Pap smears check for telltale changes in the cervix that happen after HPV infection. Over many years these changes lead to cervical cancer.
But while potentially life-saving for some women, other women can not benefit from pap smears and should not have them. A study in this issue of the Annals of Internal Medicine interviewed physicians about the kinds of patients to whom they would recommend pap smears and found that many doctors perform pap smears on women for whom it is not helpful.
Below is a summary of the U.S. Preventive Services Task Force recommendations for pap smears. More details are available by following the links below.
Like all good things, the benefit is derived from judicious use. Even though in other women the test is crucial, performing pap tests on women who can not benefit from it is just bad medicine. It falsely reassures women that they are taking care of themselves. It wastes patients’ time and scarce resources. And it ultimately decreases physician credibility.
Learn more:
U.S. Preventive Services Task Force recommendations for cervical cancer screening
Wall Street Journal Health Blog: Who Should Get a Pap Smear?
Annals of Internal Medicine article: Specialty Differences in Primary Care Physician Reports of Papanicolaou Test Screening Practices: A National Survey, 2006 to 2007
What a better topic for Halloween than fear?
All of us when hearing of a coworker or loved one who has been diagnosed with a life-threatening illness wonder if we could be next. “What if I have lung cancer? Should I get checked out? There must be some tests I can get to make sure I’m OK.” Those who take an active role in staying healthy are confident that they could do more to make sure they don’t get some dreaded disease. Most cancers, after all, are preventable, right? Or at least they can be caught early?
The scary truth is that most cancers are not preventable and can not be caught early by any test we currently have. What’s even worse, for many cancers there is no evidence that an earlier diagnosis makes any difference in outcome.
That doesn’t mean that no prevention is effective. For a few cancers (breast, cervical, colon) there are proven tests that are recommended periodically for everyone. That’s why I’m an enthusiastic advocate for colonoscopies for people over 50. Also, testing blood pressure and cholesterol in healthy people helps prevent strokes and heart attacks.
So how can we know what we should be doing to stay healthy? Should I get a head-to-toe CT scan? What about that “executive physical” with the fancy heart tests that my neighbor says I should have?
This is the job of the U.S. Preventive Services Task Force. They are the most unbiased national group that evaluates the evidence for preventive tests and treatments. Check out the links below to see what you should be doing to prevent what’s preventable. Just as important is learning what tests are unproven (or proven to be worthless). The second link, the Electronic Preventive Services Selector is especially handy. You enter some simple data about yourself and it displays all the proven preventive services for you.
That’s how you can have the confidence of knowing that you’re doing everything you can. Having tests that have been proven to be useless isn’t being proactive; it’s making an irrational decision based on fear.
There are plenty of terrible diseases out there that outmatch our best tests and treatments. But after a moment of reflection, this is not a reason to panic. It’s a reason to do what is sensible to stay healthy and then to focus on your life, not your health. The rational fear is not “What if I have pancreatic cancer?” but rather “What if I’m healthy and spend the next decade worrying about pancreatic cancer?”
Have a happy and calm Halloween. And face the future unafraid.
Learn more:
One of my goals for these posts is to use individual studies to point out the broader trends they suggest. This week I want to focus on our increasing understanding of the value of exercise after illness or injury. A generation ago a heart attack meant weeks of bed rest in the hospital followed by strict instructions from the doctor to take it easy. The weakened heart couldn’t take much exertion, we thought. Now after a heart attack patients are told to start exercising as soon as they’re out of the hospital. Similarly, patients with acute back pain were prescribed bed rest for days; now we encourage staying active and gradually increasing activity to decrease the pain.
This week the New England Journal of Medicine continues that trend for breast cancer patients. One of the most uncomfortable consequences of breast cancer surgery is lymphedema in the arm. Lymphedema is the accumulation of fluid that can happen after lymph nodes are removed during breast cancer surgery. The affected arm can become swollen, painful and prone to skin infections.
The typical advice for women with lymphedema has been to avoid weight lifting or vigorous exercise with the affected arm, fearing that this would worsen the swelling or injure the susceptible limb. This week’s study tested that assumption, randomizing women with arm lymphedema after breast cancer surgery to a group that engaged in closely supervised weight lifting and another group that did not.
Surprisingly, the women who were lifting weights had fewer exacerbations of their lymphedema, and had milder lymphedema symptoms than those who were not lifting weights. Not surprisingly, the women who were lifting weights also developed better upper body strength.
So there are increasingly fewer medical reasons to be sedentary, and we can add breast-cancer-related lymphedema to the many conditions that are improved by exercise.
Learn more:
New England Journal of Medicine Article: Weight Lifting in Women with Breast-Cancer–Related Lymphedema
CNN article: Weight lifting benefits breast cancer survivors
Cancer, Diet, New Study, Prevention
Folic acid, a vitamin found naturally in green leafy vegetables and legumes, is essential for making the building blocks of DNA. And since copying DNA is an important part of what cells do before they divide, it’s critical for cell division. Developing fetuses have very rapidly dividing cells, so it’s not surprising that folic acid deficiency has been linked to birth defects, specifically brain and spinal cord abnormalities.
To prevent these birth defects, physicians for many years have recommended folic acid supplements to pregnant women and women planning pregnancy. The problem is that folic acid deficiency harms babies in the first weeks of pregnancy, before many women know they’re pregnant and before they seek prenatal care. In an effort to end folic acid deficiency more comprehensively, the U.S. began requiring that flour and other grains be fortified with folic acid in 1998. The incidence of brain and spinal cord birth defects subsequently declined.
So if folic acid is good for pregnant women, might it have benefits for everyone else?
Well, unfortunately, no other major benefits have been found to taking folic acid supplements. Folic acid deficiency can cause anemia, but that’s rare and is easily treated (with folic acid!) when diagnosed. Back in the 1940s it was noted that leukemia patients tended to have low folic acid levels. It was hypothesized that folic acid deficiency played a role in leukemia and a trial was done in which leukemia patients were given folic acid. Surprisingly, they died sooner than the patients getting placebo. Their folic acid levels were low because it was being used up in the rapidly dividing leukemia cells; giving them more folic acid helped the leukemia cells divide faster.
Since then folic acid supplementation has been linked with other cancers. Though the findings were not definitive, given the absence of proven benefits (in those of us who are not women in child-bearing age) there is no compelling reason to recommend folic acid for everyone.
This Monday’s LA Times had two very helpful articles which summarized the controversy.
The U.S. Preventive Services Task Force (USPSTF) reviewed the evidence on folic acid and reissued their recommendations this month. The USPSTF recommends that all women planning or capable of pregnancy take a daily supplement containing 0.4 to 0.8 mg (400 to 800 micrograms) of folic acid. There is no recommendation for men or for women not in their child-bearing years.
The rest of us should probably just eat our veggies. If you do take a folic acid supplement (and I don’t) make sure it doesn’t contain more than 1 mg (1,000 micrograms) of folic acid.
Thanks to Ron T. for pointing me to the LA Times articles.
Tangential miscellany:
On Memorial Day my partner, Dr. Dorothy Lowe, and some of our staff and I will be riding in the Acura LA Bike Tour. Register to ride with us, or come out to cheer and watch the spectacle of thousands of riders taking to the streets. You don’t have other plans for 5 a.m., do you?
Learn more:
LA Times articles: Folic acid might be losing its sheen and Folic acid is important, but take care not to overdo it
About 20 years ago a blood test called prostate specific antigen (PSA) was developed with the hope that it would help in the diagnosis of prostate cancer. Since then, countless healthy men have been tested for prostate cancer with a PSA and a digital rectal exam despite the fact that there has never been convincing evidence that diagnosing prostate cancer saves lives.
The reason for the controversy about prostate cancer screening is that prostate cancer is a very slowly growing cancer which usually takes a decade or longer to be life-threatening. Prostate cancer also occurs in older men. So many cases of prostate cancer never cause symptoms and do not shorten lifespan. The treatments for prostate cancer, on the other hand, can involve serious and permanent side effects, including urinary incontinence and erectile dysfunction.
The most important question about prostate cancer screening has always been does it save any lives? And if it does, is it worth putting men through potentially harmful treatment now for the possibility that we’re saving their lives 10 years from now?
Two studies released this week in the New England Journal of Medicine unfortunately don’t help clear the fog, and have generated much media attention. (See links below.) The first study was a randomized trial in the US which showed that prostate cancer screening did not prevent any deaths from prostate cancer. This study, however, had some serious methodological flaws.
The second study randomized over 100,000 men in Europe into two groups: one which received periodic prostate cancer screening, and one which did not. The results showed a tiny mortality advantage 9 years after being screened. There was one life saved for every 1410 men screened for prostate cancer and for every 48 men treated for prostate cancer. That’s not a very compelling benefit. It means that 47 men are harmed by prostate cancer treatment for every life saved and that screening an individual has a smaller than 0.1% chance of helping him. Given this tiny benefit, it’s difficult to say if more harm was done than good.
The US Preventive Services Task Force states that the evidence is insufficient to recommend for or against screening for prostate cancer in men age 50 to 75. It recommends against screening men older than 75. For men between 50 and 75 that still means a discussion with their physicians about the possible risks and uncertain benefits of screening, and then making a personal decision without much scientific guidance.
Learn more:
NY Times editorial: The Prostate Cancer Muddle
LA Times article: Studies cast doubt on prostate cancer screenings
The US Preventive Services Task Force recommendations regarding prostate cancer screening
The two New England Journal of Medicine articles: Mortality Results from a Randomized Prostate-Cancer Screening Trial and Screening and Prostate-Cancer Mortality in a Randomized European Study