Cancer experts reassess screening tests, early detection
(CBS/AP) Cancer screening may not be so important after all. Some tumors grow too slowly to be life-threatening. Others are so aggressive that catching them early makes little difference. And today's treatments are far better for those somewhere in the middle.
Those realities are changing the longtime mantra that cancer screening is life-saving. In reality, it depends on the type of cancer, the test, and who gets checked when.
"We can find cancer early," says the American Cancer Society's Dr. Len Lichtenfeld, a longtime screening proponent. "We can reduce the burden of the disease. But along the way, we're learning our tests are not as perfect as we'd like."
Now cancer specialists are trying to strike a new balance: to stop over-promising the power of early detection and to explain that the tests themselves have risks - while not scaring away those who really need it.
Screenings for cervical and colorectal cancer may be least controversial. They spot pre-cancerous growths that are easy to remove, though even some of the tests are used too frequently. But serious questions surround other cancer-screening protocols - like which men, if any, should get a PSA blood test for prostate cancer, and whether women should start mammograms in their forties.
Also in question is whether doctors can head off another looming controversy: which smokers and ex-smokers should get a CT scan for lung cancer that is costly and prone to false alarms? A recent study showed that the scans could save lives. But guidelines aren't due out until early next year that would show who faces enough risk to outweigh the potential harm - such as an invasive biopsy to tell if a suspicious spot is cancer or just an old scar.
Current guidelines for common cancer screenings conflict. And they're written for the average patient when many people may need a customized decision, says Georgetown University's Dr. Jeanne Mandelblatt, who has studied breast cancer risk for a government panel that says most women begin screening for the disease at age 50.
Consider this, she says: The average woman has a 3 percent lifetime risk of dying of breast cancer. That's a low risk for a disease that many women find very scary. But the risk for breast cancer does gradually rise with age and other circumstances. So, Mandelblatt says, if you're 40 and have several risk factors - like dense breasts and close relatives with the disease - then you face the same risk as an average 50-year-old, not an average 40-year-old, and might consider earlier mammograms. Few primary-care doctors go into that kind of detail with their patients.
Adding to the confusion are testimonials from cancer survivors that a screening saved their lives. Dartmouth researchers recently studied how often that's true for mammograms and estimated that about 13 percent of women in their 50s whose breast cancer is detected by the tests survive as a result.
What else plays a role? Treatments have dramatically improved in recent years. And increasingly powerful mammograms are detecting more low-risk tumors, the kind that wouldn't have threatened a woman's life in the first place.
Mammograms are "not perfect, but they're the best we have," says Mandelblatt. She thinks the Dartmouth estimate is somewhat low.
PSA tests for prostate cancer are a tougher call. Last month, a government panel recommended an end to routine PSA screenings, a step further than other major medical groups that urge men to weigh the pros and cons and decide for themselves. But the U.S. Preventive Services Task Force found limited evidence that screening average men boosts survival. That's largely because so many men are diagnosed with slow-growing tumors that never would have killed them. Still, they have treatments that can cause incontinence, impotence or even lead to death.
"We really - underline the word `really' - have to pull back the messaging on prostate cancer," says the cancer society's Lichtenfeld, who himself is unsure of the test's net worth. PSA testing took off on the basis of "blind faith" that they would work, not science, he says.
"We have cells in our body that are abnormal all the time, and our bodies deal with it," he says. "Our technology takes us further and further down the early-detection path, and we need to sort through all this."