August 25, 2013

Commentary: Are all cancers equal?

Our state-of-the-art screenings find cancers that may not need treatment. But we treat them anyway, and tout our rising survival rates.

By VIRGINIA POSTREL

You're feeling fine when you go for your annual physical. But your mammogram looks a little funny, or your PSA test is a little high, or you get a CT lung scan and a nodule shows up. You get a biopsy, and the doctor delivers the bad news: You have cancer. Because you don't want to die, you agree to be sliced up and irradiated. Then, fortunately, you're pronounced a "cancer survivor." You're glad they caught it early.

click image to enlarge

Staff photo illustration/Michael Fisher

But maybe you went through all that pain for nothing.

For decades, the reigning theory has been that the earlier a cancer is spotted and treated, the less likely it is to be lethal, because it won't have time to grow and spread. Yet this theory infers causality from correlation. It implicitly assumes that cancer is cancer is cancer, even though we now know that even in the same part of the body, cancer is many different diseases -- some aggressive, some not. Perhaps people survive early-stage cancers not because they're treated in time, but because their disease never would have become life-threatening at all.

This isn't just logical nit-picking. Thanks to widespread screening, the number of early-stage cancers identified has skyrocketed. In many instances -- including types of breast, prostate, thyroid and lung cancers -- more early diagnoses haven't led to proportionate decreases in mortality. (New drugs, not early detection, account for at least two-thirds of the reduction in breast-cancer mortality.) The cancers the tests pick up aren't necessarily life-threatening. They're just really common. So more sensitive tests and more frequent screening mean more cancer, more cancer treatment and more cancer survivors.

"We'll all be cancer survivors if we keep going at the rate that we're going," said Peter Carroll, the chairman of the department of urology at the University of California at San Francisco and a specialist in prostate cancer.

In a well-intended effort to save lives, the emphasis on early detection is essentially looking under the lamp post: putting many patients who don't have life-threatening diseases through traumatic treatments while distracting doctors from the bigger challenge of developing ways to identify and treat the really dangerous fast-growing cancers.

"Physicians, patients, and the general public must recognize that overdiagnosis is common and occurs more frequently with cancer screening," argues a recent JAMA article by the oncologists Laura J. Esserman (a surgeon and breast-cancer specialist), Ian M. Thompson Jr. (a urologist) and Brian Reid (a specialist in esophageal cancer). They argue for limiting the term "cancer" to conditions likely to be life-threatening if left untreated.

That's going to be a tough change for a lot of people to swallow. For patients and the rest of the public, getting tested offers a sense of control, encouraging an almost superstitious belief that frequent screening will ward off death. (A few years ago, when the actress Christina Applegate was making the talk-show rounds urging young women to get breast MRIs, my own oncologist told me he was getting calls from women who thought the tests would not merely detect but prevent breast cancer.)

Early detection of non-life-threatening cancers also produces a steady supply of "cancer survivors," who work to support cancer charities and make their efforts look successful. There's an entire industry devoted to celebrating "breast-cancer survivors" in particular, and many women are heavily invested in that identity. It offers a heroic honorific as a reward for enduring horrible treatments. A term originally coined to remind cancer patients that their disease need not be fatal has become a badge of personal achievement.

Physicians, meanwhile, fear making a mistake. It seems safer to treat someone who doesn't really need it than to miss something potentially fatal. But, warns Esserman, director of the Carol Franc Buck Breast Care Center at UCSF, "the cancers that grow and spread very quickly are not the ones that you can catch in time with screening." If anything, emphasizing early detection misdirects research and funding. "We have to come up with better treatments, we have to figure out who's really at risk for those and figure out how to prevent them," she says. "We're not going to fix it with screening."

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