By Heather Millar
This week, the US Preventive Services Task Force (USPSTF) made headlines when it recommended that the screening blood test for prostate cancer should not be routinely given to men, regardless of age.
The task force was finalizing draft recommendations it made in October 2011, in which it said that harms outweighed the benefits of the “prostate specific antigen” or “PSA” test that can find prostate cancer before symptoms develop. The finding relied upon on two major trials of prostate screening:
• A US trial found no improvement in death rates with PSA screening.
• A European trial covering seven countries found that PSA tests conferred no benefit in five countries and prevented approximately one death per 1,000 screens in a subgroup of men aged 55 to 69, mostly in the two remaining countries.
This week, as last fall, many men and doctors reacted with anger, contending that that the new recommendation would transport men back to pre-screening days, when many prostate cancers were not found until they were advanced, and deadly.
The controversy reminds me of a similar kerfuffle over a 2009 USPSTF recommendation that most women should not begin mammograms until age 50, rather than age 40, as had been previously recommended. People also reacted with outrage to that finding, and the debate about mammograms continues.
Some commentators have begun to talk about a “backlash against cancer screening.” Some just refuse to believe the USPSTF recommendations. The debate rages over the merits of the various studies involved.
An excellent article in Tuesday’s Science Daily explores why people are often so reluctant to accept scientific findings like these.
As the Science Daily piece says, it comes down to a central conflict: Statistics versus anecdotes.
Panels base recommendations on statistics. The clinical trials that produce those statistics tend to look at things on a broad scale: a state, or even a nation, tens of thousands, or even hundreds of thousands, of patients.
Yet people base many of their medical decisions upon a sample of one: My body. My life. Or, perhaps, we’ll also consider the bodies and lives of our friends and family. I am pretty sure that a mammogram saved my life; and I have friends who still email me every time they get a mammogram, saying that my experience has “inspired” them to get the test regularly.
Likewise, I am sure that men who believe PSA screening saved their lives are not happy about this latest USPSTF recommendation. And I bet their golfing buddies will go get PSA tests no matter what the statistics say.
Does that mean that every man should get a PSA test? Or, does my experience mean that a mammogram is the right choice for every woman in her 40s?
It would be nice if things were that simple, but unfortunately, they’re not.
Both USPSTF recommendations regarding PSA tests and mammograms point out strong evidence that cancer treatments may bring very real harms of their own. For instance, nearly 90 percent of men with PSA-detected cancer will undergo treatment, including surgery, radiation, and hormone therapy. Up to five in 1,000 will die post-surgery. Between 10 and 70 men will survive, but suffer lifelong problems such as incontinence, impotence, and bowel dysfunction.
The fallout from breast cancer treatment is no less profound: Breast cancer surgery can result in “lymphedema,” painful swelling in the arms where lymph nodes have been removed. Breast reconstruction is painful, lengthy, and expensive. It doesn’t always work. Chemo and radiation increase the lifetime risk of other cancers. Fatigue, numbness, and mental fuzziness may never fully subside.
Of course, I’m not advocating that people who have cancer should not be treated. Very few of us, faced with a cancer diagnosis, are going to opt to “watch and wait.”
At the same time, though, our understanding of cancer is changing profoundly. When screening for some cancers first became possible in the 1950s and 1960s, we thought all cancers were basically the same. If we could only catch all cancers early enough, the thinking went, we were going to win the war on cancer.
In the decades since then, we’ve learned that all cancers are not created equal. A study released this spring even shows that the genetics of a cancer may even vary within the same tumor.
Prediction becomes pretty difficult in this complicated territory. Some percentage of cancers will grow aggressively and spread no matter when we find them. For those cancers, early detection doesn’t matter; they’ll kill anyway.
Some cancers will grow slowly, never needing treatment, or responding well to treatment when they’re found.
Other cancers—the ones screening really helps—may respond best if they’re found early. Alas, we don’t know which cancer is which, so we treat them all.
That’s why experts keep trying to analyze the risk versus the benefits. How many people will a screening test hurt? How many will it help?
And that’s why we patients have to keep balancing the statistics versus the anecdotes as we make our own decisions.