at Dartmouth's Norris Cotton Cancer Center, agree with this point. "It's complicated to study the effectiveness of screening," says Carney, who is also principal investigator of the New Hampshire Mammography Network, a statewide data-collection registry and research group.

"I can't tell you whether you are going to have breast cancer or not. You may have screening all your life," she points out. "You may encounter harm from screening, like unnecessary biopsies, unnecessary workup, or unnecessary radiation exposure, and I can't tell you whether we'll screen you every one to two years for the next 30 years and whether that's going to help you or not."

Where Carney and others at the Cancer Center differ with Welch and Black is on the weight they give to various studies and in their perspectives on what's best for individual patients and the general population.

"The tension that comes up with Gil's book, and with screening in general," says Carney, "is that as a policy approach you have to consider the entire population," which includes people at high risk and people at no risk and everyone in between. Until cancer researchers and physicians can predict with accuracy who is likely to get cancer, she argues, it makes sense to screen everyone.

In addition to causing harm from unneeded treatment, overdiagnosis can distort our perceptions of how well cancer treatments work, says Black. Slow-growing and potentially harmless cancers are relatively easy to eliminate, so finding and treating more of them make therapies seem more effective.

And while Welch still questions whether mammography has more benefits than harms, Carney doesn't. "At this point, the evidence is strong enough for me," she says. She places her trust in the U.S. Preventive Services Task Force, which recommends mammography screening every one to two years for women over 40. "I think if the U.S. Preventive Services Task Force has reviewed these studies as carefully as I know they do, and says it is worth doing, then that's strong evidence. . . . That's a panel of people who have looked at every single paper that's out there—not one individual who has picked and chosen what he wanted to present."

Carney believes that it is "incredibly valuable" for Welch to raise the questions he does, but, she adds, "Gil likes to stir things up."

Photos by Jon Gilbert Fox

Lisa Schwartz, top, and Steve Woloshin, bottom (center), have conducted a number of studies assessing how medical messages are communicated and how well they're understood by the public. Schwartz maintains that "scary messages" about screening are too simplistic.

Talking with Welch, it's obvious how passionate he is about the topic of cancer screening. On one recent afternoon in his office, Welch gets visibly perturbed at the mention of a mammography poster that used to be displayed at DHMC. The poster showed the silhouette of a woman with the following words in large, bold-faced type: "The greatest risk is doing nothing." And, in smaller type: "Get the facts about breast cancer."

"So whatever you do, get worried!" exclaims Welch. "That's the message. The most important thing you can do for your health is to worry about it. It's just..." he says, not finishing the thought.

"On the one hand," he continues, "I sort of accept it. I've been hearing these messages for years. But it's a little irritating, isn't it? The physicians are out there trying to get people to worry about their health." Welch believes this is the wrong approach. Instead, he'd like physicians "to get people to think positively about their health" and to move away from what he calls "medical correctness" about screening—making patients feel guilty if they choose not to pursue testing. "I object to the emerging mindset that patients should be persuaded, frightened, coerced into undergoing these tests," he writes.

Welch would like the medical and public-health communities to "turn down the rhetoric"—rhetoric like the breast cancer poster and ads that convey the message that screening could save your life.

Carney, an advocate of screening, is critical of such messages, too.

"I think a lot of public-health messages have played on the fear thing," she says. "I think that's unfortunate [because] it causes unnecessary anxiety." And, as Welch and his colleagues might add, unwarranted enthusiasm for screening.

Two of Welch's research collaborators, Lisa Schwartz, M.D., and Steven Woloshin, M.D., have been looking at how medical messages are communicated to the public for the past 10 years and have found that Americans are extremely pro-screening. In a 2004 study that was published in the Journal of the American Medical Association (JAMA), Schwartz and Woloshin showed that approximately 87% of adults believe routine cancer screening is almost always a good idea and about 74% believe that finding cancer early saves lives. (See the graph here for a visual representation of some of the data that appeared in this paper.)

"Less than one third believe that there will be a time when they will stop undergoing routine screening," the authors wrote. And "a substantial portion believe that an 80-year-old who chose not to be tested was irresponsible: ranging from 41% with regard to mammography to 32% for colonoscopy."

Schwartz, Woloshin, and Welch, along with several of their colleagues who work at the VA Medical Center in White River Junction, Vt., make up the VA Outcomes Group, a collaboration of physician-researchers who are concerned with what they perceive as excesses in American medicine. "We question the assumption that patients always stand to gain from having more health care," the group states on its web site. "We are concerned about advertising and other messages that exaggerate the benefit of health care and minimize the harm (or ignore it entirely). And we are troubled by the increasing enthusiasm for seeking diagnoses in the well and initiating interventions for those identified as 'sick.'"

Many public messages about screening communicate two things, says Schwartz: "It's really dangerous if you don't" get screened and "this is what a good person does." Framing the decision to be screened or not in a moral context makes it "harder for people to make an informed decision," she maintains.

"We have given people persuasive, scary messages for a long time to tell them that earlier is better," explains Schwartz, who codirects the VA Outcomes Group with