The false positive of preventive care

My first routine screening mammogram led to a fluoroscopically guided biopsy. My chin and ear were jammed into a table, near a hole through which my breast hung, compressed beyond recognition by two Lucite sheets. Then a needle penetrated the sensitive tissue.

“Where the heck did that calcification go?” the radiologist said. “Snap another picture.”

As a physician, I minded the pain and compression less than the “snapping of the picture,” which shot another dose of radiation into a delicate organ that had already absorbed much more of it than I would have liked. All I could think was, I should have known better.

A recent study in the prestigious British Medical Journal reported on 25 years of Canadian evidence about the effectiveness of mammograms, with results that will be startling to many. After following 90,000 women between the ages of 40 and 59 who had been randomized to receive or not receive mammograms, the study found no significant difference in the rates of death from breast cancer in those who did or didn’t receive the scans. More cancers were found, but lives weren’t saved. Statistical analysis suggested that 1 in 5 of the discovered breast cancers were “overdiagnosed” — in other words, they were so indolent that they would never have posed a danger to the woman’s health, even if they had been left undetected and untreated. These women were subjected to surgery, and sometimes radiation or chemotherapy, without any benefit. For the other women, it appeared that slightly later detection (once the lump could be felt on a manual breast exam) didn’t significantly worsen their odds of survival. There has been a dramatic overall reduction in breast cancer deaths over time, but the BMJ data suggest this is due to more effective treatments, rather than early detection.

It is an old truism that “an ounce of prevention is worth a pound of cure” — but what if it isn’t worth it? In recent years the effectiveness of many screening tests has been called into question. These include annual Pap smears that test for cervical cancer in low-risk women (every three years probably works just as well), screening electrocardiograms for heart health, prostate screenings in men (harm from unnecessary surgery and procedures may outweigh any benefit from early cancer detection) and bone density tests for osteoporosis in low-risk women under 65. Intuitively, it’s hard to argue with the idea of proactive health care; we’d all like to prevent problems before they get started, and catching things early seems as though it should be both cheaper and more effective. Certainly, prevention in the form of good health habits — say, healthy eating and exercise — has many benefits and no downsides. But tests, much less procedures, are a different story.

“How can it hurt?” many of my patients ask, rhetorically, referring to a mammogram or other screening test. The answer is, in lots of ways. Cost is the simplest reason and it shouldn’t be dismissed; tens of millions of dollars are spent annually on these tests, which is still only the tip of the iceberg when other costs (from unnecessary surgery, chemotherapy or follow-up testing) are considered. But beyond cost, there are health harms as well. A false positive test (defined as an abnormal result when disease is not present) can lead to biopsies and surgeries, which have a low but real rate of serious complications, such as infection, anesthetic reactions and bleeding. Repeated scans involving ionizing radiation (such as mammograms, X-rays and CT scans) can also increase the risk of future cancers; we’re not yet able to quantify this risk, but it may prove to be substantial. Then there are the psychological implications: the pain of the biopsy or surgery, the anxiety of waiting for the result and the possibly life-altering experience of getting a cancer diagnosis that may not have been entirely necessary.

Discussion of screening (and breast screening in particular) can be highly emotional. Everyone has heard stories of patients who weren’t screened and died from breast cancer, and others whose cancers were caught on mammogram and survived. It is impossible to tell, though, how many in the former group would have died anyway, and how many of the latter would have survived without the test. It’s a political topic as well, linked to women’s rights and needs. The U.S. Preventive Services Task Force — an independent panel of medical experts that evaluates scientific evidence for preventive procedures —reviewed the evidence for mammography in low-risk women under 50 in 2009, and concluded that, to the best of current knowledge, it provided no benefit. The resultant uproar by screening advocates — who often drew on anecdotes and emotional arguments, rather than data — caused the recommendation to be withdrawn and replaced by a tepid, neutral stance on mammograms in this subset of women. Other major U.S. medical organizations’ recommendations vary: for women 40 to 50, some say the test should be done every year or every two years, while others say it shouldn’t be done at all. The new data will raise the question of shifting the age to 60.

I have a mild family history of breast cancer, which put me in a gray zone on the testing recommendations. (If a woman’s baseline risk is elevated due to family history or other factors, the benefits of screening increase dramatically.) So at the age of 41, I hesitantly scheduled an appointment. I had calcifications, which led to an immediate biopsy. There were multiple needle passes and more fluoroscopic X-rays than I could count. Ultimately, the pathology was benign. The swelling, bruising and pain lasted for three weeks. The price tag was more than $2,000 (all out of pocket on my high-deductible plan). Worst, I wonder whether someday I might have a cancer caused by all those X-rays. No one could tell me how much radiation I had been subjected to; the tech breezily said, “If it causes a cancer, it won’t matter because we’ll catch it early on a later mammogram.” I know it’s not a high risk — but I wish I hadn’t taken it at all.