Celebrities keep pushing for more cancer screening. This Dartmouth professor makes the case for less.

Lately, celebrities like Taylor Swift and Rita Wilson have been offering a seemingly innocuous bit of health advice to the public — everyone should get screened for cancer early and often. It might just save your life.

But this advice actually contradicts what the best available evidence tells us. When it comes to cancer, more health care isn't necessarily better. That's the difficult message Dr. Gilbert Welch, author of Less Medicine, More Health and a Dartmouth physician, has been trying to get through for years.

Gilbert Welch, a Dartmouth professor who argues less cancer screening is better.

Over a decade ago, Welch started looking into the effects of mass screening programs for cancer that have emerged around the globe. These programs take otherwise healthy people and subject them to tests to find out whether they have lumps and bumps that may be malignant. This is different from using ultrasounds or other technologies to diagnose people at risk of a disease or who have symptoms that require investigation. It's the type of preemptive screening that so many celebrities advocate.

Welch found something surprising: in many cases, screening wasn't actually helping people or saving lives. The programs were turning healthy people into cancer patients unnecessarily, leading them to needless treatment and hospitalization, creating clubs of "cancer survivors" who actually would have lived even if their cancers were left untouched.

I spoke to Welch about how many of our assumptions about cancer screening are wrong, the cancer myths people buy into, and how celebrities only exacerbate the misunderstanding.

Julia Belluz: Another day, another celebrity diagnosis and more health advice. Rita Wilson this week, Taylor Swift last week, Angelina Jolie last month. What do celebrities get wrong about cancer screening?

Taylor Swift. (Andreas Rentz/Getty)

Gilbert Welch: It all centers on the assumption that more medical care is always better for you. I don't blame people for this belief, because it's the message they've been hearing for years: engaging the system to look for things that are wrong can only make you healthier.

The disturbing truth is that we have exaggerated the benefits of medical care, and we've underplayed — or ignored entirely — the harms. This is particularly true when it comes to early detection.

JB: What is the public failing to grasp about screening when we continually buy into the aggressive diagnosis and treatment narrative?

This chart shows that while more thyroid cancers were diagnosed in South Korea after a mass screening program was introduced, it didn't actually improve the mortality rate. (New England Journal of Medicine)

GW: The assumption that sooner is always better is particularly strong for a feared disease like cancer. That's why screening always sounds like a good idea. But our understanding of cancer is changing: it is a much more diverse set of diseases than we previously thought.

We used to think that the minute a cell became cancerous, it was something that was going to kill you if we didn't do anything. That kind of definition is still in some medical dictionaries. And that definition was actually fairly accurate for the kinds of cancers we found in the 1950s and '60s. But now, as we look for early forms of the disease, we realize there's a whole bunch of heterogeneity.

JB: So a lot of our mistaken assumptions about cancer screening rest on erroneous beliefs about the disease?

GW: Yes. The old view is being replaced by a new conceptual model of cancer — what you might call the barnyard pen of cancers. There are three animals in the barnyard: birds, rabbits, and turtles. The goal of early detection is to fence them in. But you can't fence in a bird; it‘s already flown away. Birds represent the most aggressive cancers, the ones that have already spread by the time they are detectable.  Screening can't help, so the question for the birds is can we treat them.

The rabbits are ready to hop out at any time. They are the potentially lethal cancers, cancers that might be helped by screening. Then there are the turtles — the cancers that aren't going anywhere anyway. These are small, indolent cellular abnormalities that meet the pathological definition of cancer under the microscope but never cause problems. Screening is really good at finding turtles.

Harding Center for Risk Literacy

Mammography didn't improve the rate of breast cancer death. (Harding Center for Risk Literacy)

Screening may help a few, there's no question. But people need to know both sides of the deal. They need to recognize that all the screening survivors in the media, particularly in breast, thyroid, and prostate cancers, are much more likely to represent the harm of screening — unnecessary diagnoses that were never going to bother anybody — than the benefit of screening, or someone who has actually been spared a cancer death.

JB: Most people would say it's better to be safe than sorry. What are the downsides of being a patient unnecessarily? Why does it matter?

None of us wants to be made into a cancer patient unnecessarily GW: None of us wants to be made into a cancer patient unnecessarily. Treatments can be hard on people. And then there's the question of all the additional procedures associated with screening — not to mention the anxiety, which can't be good for your health.

I understand that patients would rather be safe than sorry.  Unfortunately it's not clear which course of action is reliably "safer," nor which one is more likely to make you "sorry."

JB: Why doesn't that message get through?

GW: It's beginning to. We are in the process of a major course correction. More and more doctors understand the problem. Prostate cancer has become the poster child for the problem. Overdiagnosis is now recognized in breast, lung, kidney, and thyroid cancer, too. So we're in the midst of a course correction, but medical course corrections take a lot of time. And these are not easy issues for doctors to broach with patients in a 10-minute clinical visit.

JB: Celebrities don't communicate the overdiagnosis message, either. They usually stick by the "screen early, screen often" adage.

GW: It's so much more than the celebrities. The audience is primed for the message. They're getting these message all the time, whether from academic medical centers, from people who make the tests, the media who presents a simple story — a new cancer test that finds even more cancer. But the best test is not the one that finds the most cancer; the best test is the one that finds the right cancer.

JB: How can patients apply this insight in their lives in a practical way? Does it mean opting out of routine screening if you're not at a high risk for a particular cancer?

GW: Everyone needs to have a more balanced view of medical care. For years, we focused on the problem of too little medical care. But now we recognize there can be too much. When it comes to early diagnosis, the real side effect is that it can needlessly turn people into patients. When we look for early forms of any disease, we find a new group of patients who otherwise we'd never find: patients who are not destined to develop clinical disease. People should understand those most likely to benefit from early detection are people at the highest risk of disease — people like Angelina Jolie.

JB: What did you make of Angelina Jolie's public service messages about cancer screening given her own double mastectomy and oophorectomy?

Angelina's latest New York Times op-ed.

GW: I thought she was trying to be balanced. In her first New York Times op-ed, it wasn't sufficiently clear that her situation did not apply to 99 percent of American women. But in her second, I think she's sharing a hard decision for a very narrow group of women.

Everyone should understand that Angelina Jolie is a special case. She's a special case because not only does she have the BRCA-1 mutation [that puts her at a higher risk for breast and ovarian cancer], but she also has a really strong family history. Most people should say, "I'm glad I'm not Angelina," because most people are not in that situation.

JB: Is it fair to say most people are at a below-average risk of developing a particular cancer? Because that's another message that's different from what many of us are made to believe.

GW: Yes — let me explain why. If you imagine a distribution with a really long tail, the high-risk people are very high risk. It's not a bell-shaped curve of risk. It has this long upward tail of people at really high risk, and the average of that distribution is well above where the typical person is, because it's been drawn up by the people at very high risk. For the mathematically inclined, it's the difference between the mean and median.

JB: What do you wish people understood about cancer screening?

GW: I'd like people to understand why a more balanced view of medical care is in their interest. That's what my whole book Less Medicine, More Health is about: how to deal with those assumptions a lot of people have been taught.

When it comes to early detection, they should recognize that the side effects of screening — false alarms, more diagnostic procedure, and more needless treatment — are actually more common and more certain than the benefits.  The key questions to ask is: how sure are you about the benefit, and how big is it? What are the associated harms? Then decide, knowing that screening is a choice and not a public health imperative.

JB: You've sort of made a case against mass cancer screening. So what would you like to see instead?

GW: I'd like to see preventive medicine move away from mass screening and toward health promotion. Health promotion is fundamentally a positive strategy, one your grandmother might have told you: get plenty of sleep, eat your fruits and vegetables, go play outside — and don't start smoking. Take care of yourself. But it's hard to promote health when we are constantly looking for things to be wrong.

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