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What You Should Know Before Being Screened for Cancer

Estimated read time: 7-8 minutes

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It is one of those things that just seems to make sense: If your doctor offered you a test that could show whether you had cancer -- a test that might save your life -- you'd want to take it, right?

Every year, tens of millions of Americans line up for mammograms to detect breast cancer, colonoscopies to root out colon tumors, and blood tests to hunt for markers of prostate cancer.

But now, building on the concerns of other researchers, several Dartmouth Medical School doctors have embarked on a crusade: They are urging patients to become savvier about all that poking and probing, and helping them understand that the screens carry potential risks along with benefits.

"I'm not sure it's always in an individual's best interest to go looking for things to be wrong," said Dr. H. Gilbert Welch, of Dartmouth and the Department of Veterans Affairs. "We're in this culture of uncritically valuing any diagnostic test, and the truth is, testing is a two-edged sword." Welch, who recently wrote a book on the topic, and his peers at the medical school don't want people to reject cancer tests outright, just to recognize that they can sometimes cause false alarms, miss cancers, and identify cancers that will not turn deadly.

Cancer doctors agree that screening tests are imperfect tools. But those doctors, who regularly face desperately ill patients, insist that the screens save lives.

"The early prevention and treatment of cancer must remain one of our highest societal goals," said Dr. Howard Koh, an oncologist, epidemiologist and associate dean at the Harvard School of Public Health. "I got into this field because, like all physicians, I have treated too many patients who have suffered deaths because of preventable cancer." It's widely accepted that people with signs of cancer or an extensive family history of the disease should be tested. Where the Dartmouth doctors depart from the medical establishment is on this point: Should everyone be screened, or just those with symptoms and significant risk factors for the disease?

Does a trim 55-year-old woman with no family history of breast cancer really need to undergo a mammogram? And what about her similarly healthy 65-year-old husband? Should he agree to be tested for prostate cancer?

Screening can sometimes suggest the presence of cancer when there isn't any. That can result in a cascade of increasingly invasive tests and potentially life-threatening treatment. And no cancer screen can tell patients whether a mass will turn deadly or linger harmlessly.

Screening tests are best at detecting those cancers that are least dangerous -- the slow-moving kind. The more-lethal tumors, those that grow swiftly and spread rapidly through the body, can develop between screenings.

This is hardly the first time cancer screening has been the center of controversy. For much of the past two decades, debates over mammograms, the most exhaustively studied cancer screen, have pivoted on whether women should start getting tested at age 40 or 50. And in 2001, a Swedish study contradicted previous research showing that early detection helped patients beat breast cancer, and set off a continuing debate.

Concerns have been raised, too, about whether a common exam for prostate cancer, the prostate-specific antigen, or PSA, creates too many false alarms. Prominent medical associations disagree on who should be screened and when.

And some tests, including colonoscopies, can make healthy people sick.

The colon test, which involves threading a scope through the intestines, can in rare cases rupture the organ.

The truth is, there's still debate on the best age to begin mammograms, and on how many lives the PSA test saves. Mammogram studies have reached conflicting conclusions, and the first rigorous scientific look at the prostate screen won't be completed for a few more years. While deaths from prostate cancer have dropped since the early 1990s, there's no proof that the PSA is responsible.

Not all cancer tests are created equal -- and there aren't any screens at all for some of the deadliest tumors, those that attack the lungs, pancreas and ovaries.

"Just because screening works for one cancer doesn't mean that it's overnight going to work for every cancer," said Dr. Graham Colditz, director of the Center for Cancer Prevention at the Harvard School of Public Health. "It's not a simple piece of math that is the same for every cancer or every screening test." Consider the Pap smear, long a staple of gynecologic visits and the most widely used cancer screen. Oncologists hail it as the sterling example of what screenings can do at their best. The Pap, which involves analyzing cervical cells for the earliest signs of potential disease, catches precancerous growths before they turn into tumors.

Since the test came into widespread use, deaths from cervical cancer have plummeted, with studies showing a decline of nearly 80 percent since the 1930s.

The PSA test for prostate cancer, by contrast, shows the limitations of some screening techniques. While elevated PSA levels can indicate the existence of cancer, they can also be reflective of an enlarged prostate, a common, and harmless, consequence of aging. But there's no way to make that distinction without performing an uncomfortable biopsy. And even if the biopsy comes back positive, is there value in telling a 75-year-old man he has prostate cancer? Given that the disease grows quite slowly in most men, is surgery that can result in lost bladder control and sexual function warranted?

"Our threshold for instituting these tests as part of routine practice should be higher," said Dr. Lisa Schwartz, also of the VA and Dartmouth Medical School, who has published medical studies on what she considers the overuse of cancer screening. "We're just saying: 'Be honest with people about what screening can and can't do and the potential harms.' There have been very persuasive campaigns where people feel it's an obligation to screen." Sometimes doctors are not as cautious in using test results as they should be before beginning treatment, said Robert Smith, director of cancer screening at the American Cancer Society and a staunch advocate of screening.

"The issue of overtreatment -- and it's a very real issue -- does not need to be laid at the feet of screening," Smith said. "It needs to be laid at the feet of therapeutic decisions made by doctors." Part of the problem is that detecting cancer isn't always straightforward. Reading mammograms, for instance, is an art that requires considerable training, Smith and others said, and patients might want to get a second opinion.

"There's a broad range of quality in cancer screening," Smith said.

"With mammography, overall accuracy is pretty good, but there is a considerable range of skill in radiologists reading mammograms." Both supporters and detractors of screening acknowledge there is an expense to a patient's well being and psyche, in addition to the nation's health-care system. The cost of a PSA blood test is quite modest, but colonoscopies can run $1,000 a pop, almost always picked up by health plans.

"If you really did" give everyone over 50 a colonoscopy, said Dr.

Harris Berman, former chief executive officer of the Tufts Health Plan, "the cost to the health-care system would be enormous." Fundamentally, for patients, the question over screening comes down to this: Should I get tested for cancer?

The decision requires active communication between doctors and patients, a better recognition of the limitations of the test, and an understanding of personal risk for getting a particular cancer.

"I'm certain there are people who are unhappy about the discomfort, the worry, the expense of going through unnecessary procedures," said Hester Hill Schnipper, chief of oncology social work at Beth Israel Deaconess Medical Center. "I'm sure in most people, though, that's more than balanced by the good news at the end." Stephen Smith can be reached at

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c.2004 The Boston Globe

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