October 22, 2013
News Review From Harvard Medical School -- Few Doctors Explain Harms of Cancer Tests
A survey suggests that most doctors aren't telling people about the possible harms of cancer screenings. The study was based on an online survey. It included 317 men and women, ages 50 to 69. Only 9.5% said their doctors had told them that cancer screening tests can lead to overdiagnosis and overtreatment. These possible harms include follow-up tests for abnormal results that turn out not to be cancer. People also may get treatment for cancers that were unlikely to cause harm in their lifetimes. About 80% said they would have wanted to know about these risks before getting screened. People also were asked how much overdiagnosis was OK when weighed against possibly catching a cancer early. The answer depended on whether they were already getting the tests. About half said they would not start a screening program that led to even 1 case of overtreatment for each life saved. But 59% said they would continue current screening tests even if they led to 10 cases of overtreatment for each life saved. The journal JAMA Internal Medicine published the study. HealthDay News wrote about it October 21.
By Howard LeWine, M.D.
Harvard Medical School
What Is the Doctor's Reaction?
The potential to save lives with cancer screening has been widely promoted. And it's generally accepted as beneficial without risks. Doctors also have bought into this notion.
But in fact, screening often leads to overdiagnosis and overtreatment. In this study, only 9.5% of people said their doctors had told them about these risks. But 80% of them said they did want to be informed of the possible harms before having the screening test.
I am surprised by these results. In recent years, there has been a lot of debate about the usefulness of screening tests and their potential risks. I would have expected more doctors to discuss the potential downside of cancer screening.
Of the common cancer screening tests, experts disagree most about routine prostate cancer screening. In fact, now the general advice is for doctors NOT to order a blood test for PSA (prostate-specific antigen) without first discussing the pros and cons. And the highly respected United States Preventive Services Task Force advises against screening men at average risk of prostate cancer.
A mammogram every year or every other year has broader acceptance for women age 50 and older. But some studies suggest that life-saving benefits of mammography are overstated. And doctors rarely discuss the risks before they order a mammogram. The risks include finding spots that aren't cancer. Or the test could find spots that are cancerous but would never have caused harm if left untreated.
In contrast to prostate and breast cancer screening, more solid evidence supports screening for colorectal and cervical cancers. Very few experts suggest we should not be doing these tests.
The reason for this difference is that PSA tests and mammograms don't prevent cancer. They only detect early cancers. Colonoscopy and cervical cell sampling (Pap tests) detect more than just early cancers. They also detect polyps and pre-cancers. With removal or other treatment, cancer can actually be prevented.
What Changes Can I Make Now?
Cancer screening promotion has overshadowed the importance of cancer prevention.
Here is what you can do to help lower your cancer risk:
- Maintain a healthy weight.
- Don't smoke or use other tobacco products.
- Either avoid alcohol or drink an average of no more than one alcoholic beverage per day.
- Avoid binge drinking, even if the average amount of alcohol you drink is moderate.
- Eat a diet rich in vegetables, especially the green leafy ones. They are rich in folic acid. For women, folic acid may offset any increased risk of breast cancer if you drink alcohol.
- Increase your fiber intake. It may lower your risk of colon cancer.
Stay physically active, and try to find time every day for dedicated exercise. Aim for at least 150 minutes of exercise per week.
What Can I Expect Looking to the Future?
Cancer screening is already tailored somewhat to personal risk. People with a family history of certain cancers need to start screening at earlier ages than the general public. They also should be screened more often and may require different types of tests.
In the future, genetic testing will guide most screening advice. But it will never replace the importance of preventing cancer and other diseases with healthy lifestyle choices.