Cancer screening saves lives. You hear it all the time. But our aggressive search for cancer has a downside, too.
"When we look hard enough, and we are getting better and better at looking hard, ultimately we realize that a whole bunch of people have cancer, but not all of those cancers are going to matter to them," said Dr. Gilbert Welch, a professor of medicine at the Dartmouth Institute for Health Policy and Clinical Practice.
Welch, a medical doctor, authored "Should I Be Tested for Cancer? Maybe Not and Here's Why," and he is writing another book about overdiagnosis.
"Overdiagnosis is when we give a patient a diagnosis for something which they would never develop symptoms or die from in their normal life spans. They would otherwise never know about it," he said.
Welch argues that early screening may help some people avoid premature death, but it causes others to be thrust into uncomfortable and unnecessary medical treatments when they otherwise would have died from other causes, with no symptoms of certain cancers.
"We've really systematically overstated the benefits of screening and we've really denied that there is a downside," Welch said.
The medical community viewed Welch as a pariah when he first published his analysis of early screening a dozen years ago, but developments in prostate cancer screening have changed perceptions. In August, the U.S. Preventive Services, the federal board that sets standards for preventive medical practices, changed its guidelines on who should be tested. The board recommended that men older than 75 should not be routinely tested for prostate cancer, an acknowledgment that an older man with prostate cancer is more likely to die of something other than the cancer.
"There's a lot of innocuous prostate cancer out there, and a fair number of the public recognizes this," Welch said. "What is less understood is that this is not something restricted to prostate cancer screening. It's evident in other cancer screening as well."
But cancers don't come with a business plan, said Dr. Robert Smith, director of screening for the American Cancer Society. Modern medicine doesn't have the sophistication needed to pick out a deadly cancer from a harmless one.
"We do know that overdiagnosis occurs. It's a statistical phenomena and it's part of screening," Smith said. "The overwhelming majority of people diagnosed with an invasive cancer do not have one that is non-progressive and it will be very nice when we can figure out who does and who doesn't. They are a very small number almost certainly. The only real option you have when you are faced with a disease that can be life threatening is to treat it as early as possible."
The likelihood of getting cancer is high. Every one in two men will have cancer in their lifetime and every one in three women will be diagnosed with cancer, according to the American Cancer Society.
Early cancer screening is designed to find a few people who have cancer from a large pool of healthy people that don't. Invariably, the tests find some serious cancers, but they also miss some, give false positives and overdiagnose some. Most people, however, are cancer free and are told so, Smith said.
"You have to think of screening as something that needs to be much better than it is," Smith said. "We need to improve screening so we maximize the benefits and minimize the harms, the inconveniences, the expenses and the stress."
The American Cancer Society prominently touts the improved survival rates and credits early screening.
But those numbers are misleading, Welch said.
Survival statistics are based on the date of diagnosis. So, if the diagnosis is made earlier, then survival rates automatically look better regardless of whether the person actually lives longer. It's called "lead-time bias."
"If you have a man who dies at 70, if he is diagnosed at 67, he only survives 3 years. It doesn't reflect well on survival statistics," Welch said. "If he's diagnosed at 63, he survives seven years and he makes the five-year survival rate look good. What's changed? Nothing. The time of death is exactly the same. The only thing that's changed is you've advanced the time of diagnosis."
Welch said survival rates are also inflated by the rising number of innocuous cancers being added to the mix. It makes it look like more people are beating cancer, when they never really had to fight it.
Smith countered that success of early screening is measured by death rates, not survival rates. And in many cases, death rates are falling. Death rates for breast and prostate cancer have been declining since the early 1990s. Cervical cancer, which is screened through Pap tests, dropped 67 percent over three decades. Colorectal deaths are declining, and the death rate for melanoma has decreased dramatically for people younger than 50, according to the American Cancer Society.
Though, it's impossible to separate the effects of early detection from the effect of improved medical treatments on death rates.
The number of people overdiagnosed varies depending on the accuracy of the screening test, Welch said. It is low in colorectal and cervical cancer screening, but Welch said overdiagnosis could be as high as 25 percent in mammography and higher for prostate screening. Results from a major study on prostate cancer screening are expected in two years and will help sort out how beneficial prostate screening really is.
So what does all this mean for you, the individual? It depends on how much you are willing to risk.
Welch doesn't tell people to not get tested. He just wants them to know the downside, he said.
"It's a bit of a gamble either way," he said. "You may be helped, you may be hurt. Some are eager consumers of medical care. Others say 'If it's not broke, don't fix it.' "
The gamble is too great not to be tested, Smith said. For some severe cancers, a late diagnosis is almost certain death.
Cancer screening is like insurance, he said.
"We insure our cars and homes not because we expect to wreck them or for them to burn down," Smith said. "We do it against the low likelihood but the potentially catastrophic likelihood that something unexpected would happen."
Inside Dr. Hugh A. G. Fisher's office the patients usually opt for the test.
"We are a country that likes to be screened for cancer," said Fisher, a uro-oncologist at Albany Medical Center. "A lot of people ask for (prostate screening) even if we tell them we don't know if it prolongs survival at this point. We don't even know if it improves mortality. They'll say I'll take it."
Older men want it too, Fisher said.
"At age 75, we may say we are not going to do it, but then they'll say 'Why?' " Fisher said. "Well, because the actuarial tables say you are going to die in 10 years. So the average 75 year old is going to say 'I'm not going to die in 10 years. I'm going to live to 95.'?"
Gert Colgan, a breast cancer survivor and program director at the Capital Region Gilda's Club, said testing let's you make informed decisions. Gilda's Club is a nationwide support group for people affected by cancer.
"I want to know what's going on inside my body so I can maximize my life as I live the rest of it," Colgan said. "I would be one of those people who want to know."
Cathleen F. Crowley can be reached at 454-5348 or by e-mail at ccrowley@timesunion.com.
American Cancer Society guidelines for the early detection of cancer
Recommendations for healthy people at average risk for cancer:
Breast cancer: Yearly mammograms are recommended starting at age 40 and continuing for as long as a woman is in good health.
Colon and rectal cancer: Beginning at age 50, both men and women at average risk for developing colorectal cancer should use one of the screening tests: flexible sigmoidoscopy every 5 years, colonoscopy every 10 years, double contrast barium enema every 5 years, CT colonography (virtual colonoscopy) every 5 years, fecal occult blood test (FOBT) every year, fecal immunochemical test (FIT) every year, stool DNA test (sDNA), interval uncertain. A colonoscopy should be done if test results are positive.
Cervical cancer: All women should begin cervical cancer screening about 3 years after they begin having vaginal intercourse, but no later than when they are 21 years old. Screening should be done every year with the regular Pap test or every 2 years using the newer liquid-based Pap test.
Prostate cancer: Both the prostate-specific antigen (PSA) blood test and digital rectal examination (DRE) should be offered annually, beginning at age 50, to men who have at least a 10-year life expectancy.
Lung cancer: No reliable screening test is available so screening is not recommended.
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