Here's an unabashed plug for a feature in our April issue—already in your hands if you're a subscriber, and coming to newsstands any day now if you're not. The article is called "What's Wrong With Cancer Tests," and it raises some very unsettling questions about screening tests like mammography, colonoscopy, and PSA testing ... and, indeed, the whole notion of screening people for cancer. This article gores sacred cows right and left: Its basic claim is those tests aren't nearly as effective as most people believe, and a whole lot riskier. Maybe the most shocking thing of all is that many top cancer experts agree with that claim.

The piece was written by Shannon Brownlee, author of last year's book, Overtreated: Why Too Much Medicine is Making Us Sicker and Poorer—a best-seller and, even more important, highly respected by medical researchers, not to mention economists. Shannon has generously agreed to guest-blog periodically while this issue is on newsstands. She's also hosting a discussion about this topic—please head over here to ask questions and share your thoughts!

And now, here's Shannon:

Why would a medical writer want to suggest that people shouldn't necessarily get screened for cancer? After all, I and my fellow reporters have spent the last three decades urging readers to get their mammograms, colonoscopies and Pap smears. My first clue that maybe we in the media should dig a little further before making such blanket recommendations came about a decade ago, when I was on staff at U.S. News & World Report.

In reporting a story about cancer, I happened to talk to a researcher at the National Cancer Institute, who told me that there was a lot of controversy around the Prostate Specific Antigen, or PSA test. More and more men were taking this simple blood test to see if they had early stage prostate cancer. The National Cancer Institute researcher told me that the test wasn't as great as everybody thought it was.

So I did what any good reporter does - I began asking him and other doctors and researchers a lot of questions. It turned out he was right. There was (and still is) a lot of controversy around the PSA test. What's more, much of the evidence suggested that it wasn't reducing men's risk of dying of prostate cancer —which is the point of screening tests.

I turned the story in, and to my surprise, my editor told me to rewrite it. Why? Because he just couldn't believe that what I had found could be true. The magazine printed the story in much watered down form, but I knew my reporting was solid.

Not long after that, my 70-year-old father called me and told me his PSA test had come back high. His doctor wanted him to get a biopsy. What should he do?

I sent him to a doctor I had interviewed for the story, who happened to practice in Portland, Ore., near where my parents live. That doctor was able to explain to my dad what the evidence said about prostate cancer and PSA testing. My father decided not to get a biopsy, which can be painful and lead to serious infection. He's still alive today and glad he didn't go through it.  (If I'd known about patient decision aids, I would have sent him one.)

That's when I began to think that screening might not be right for everyone. It was also the moment when I started to understand that there was such a thing as too much medical care.

For anybody who has spent time in the hospital, either as a patient or as a family member of somebody who is seriously ill, that might seem pretty obvious. Many of us have wondered if all those CT scans, blood tests, drugs, and (often painful) procedures were really necessary. A lot of them aren't. In fact, about a third of the money we spend on health care—$600 to $800 billion—goes toward tests, surgeries, drugs, procedures, and time in the hospital that does nothing to improve our health.

Eventually I wrote Overtreated: Why Too Much Medicine is Making Us Sicker and Poorer. I wrote it for my parents, to help them make choices about their own care. I had the same motivation for this article—and I hope it helps you, too.