Dr. Marie Savard Explains Why Some Cancer Screenings May Do More Harm Than Good
Marie Savard, ABC News, Nov 17, 2009
Screening tests for early detection of cancer have undergone a lot of scrutiny lately. Just a few weeks ago the American Cancer Society (ACS) issued a press release reminding us that the Cancer Society may have overstated the benefits of screening and underemphasized the potential harm when it came to testing for early breast and prostate cancer.
The ACS went on to discuss the limitations of screening women for early breast cancer with mammograms and screening men for prostate cancer with the simple PSA blood test.
This week, the United States Preventive Task Force (USPTF) issued new guidelines for breast cancer screening. I suspect that explains why the ACS issued its recent comments, knowing these guidelines were about to be released.
The USPTF analyzed various mammography screening schedules and concluded that:
1) Women under the age of 50 should not be screened with routine mammograms because proven benefits are lacking and the risks of harm (such as unnecessary biopsies from false positive results, especially in women with dense breasts) are greater.2) Screening women of average risk between the ages of 50 and 74 with mammography every two years will achieve most of the benefits of yearly screening, but with less harm.
3) The task force also recommends against teaching breast self-exam.
So why the new recommendations? What new information do we have on the behavior of breast cancers and mammograms?Many scientists believe that there are two types of cancers.
First there are those that appear suddenly, grow rapidly, act aggressively, and often are diagnosed when it is already "too late" for curative treatment. Even a yearly mammogram might not diagnose this aggressive breast cancer in the early stages.
But for many women (and men when it comes to the prostate) their cancers are of a second type -- they are very slow growing, often not even showing up on mammograms for many years. These slow cancers are thought to be much less aggressive. Some experts are even suggesting that these cancers may either disappear on their own or would not cause injury or death to the person with them, even without treatment.
Can Cancers Disappear on Their Own?
A recent study in the Journal of the American Medical Association (JAMA) pointed out the evidence for this. Breast cancer statistics for women in the Unites States has not shown a reduction of advanced breast cancers being diagnosed, despite the widespread use of mammography.
One would expect that if mammograms diagnosed breast cancers earlier and women were then treated for these cancers, over time there would be a reduction in the diagnosis of more advanced cancers from the "successful" screening. But this is not the case. Advanced cancers continue to be diagnosed with greater than expected frequency.
For men, the same seems to be true for prostate cancers. Many men will develop prostate cancer if they live long enough, yet many of these cancers will not cause problems and don't need to be treated. However the simple PSA blood test, like the mammogram for women, does not distinguish the slow growing from the more aggressive fast growing ones.
On the other hand, for both men and women who are equally at risk for colon cancer, screening and early diagnosis and treatment has led to a significant reduction in the number of more advanced cases of colon cancer diagnosed. So when it comes to colon cancer, early detection and removal of any precancerous polyps or early cancers really make a difference.The same is true for Pap tests in women. Pap tests are also a great screening success story (read my recent blog on the value of adding the HPV test to your Pap test if you are 30 or older). Women who have an abnormal Pap test will have their abnormal cells diagnosed and treated early and are therefore much less likely to be diagnosed with advanced cervical cancer.
Australian researchers have found that as many as a third of women diagnosed with breast cancer may not need treatment. The researchers from the University of Sydney say they found that screening with mammograms is far from perfect and women often go on to have surgery and chemotherapy that is unnecessary because the cancers detected are slow-growing and not life-threatening. Unfortunately, our current screening with mammography -- even the more detailed digital mammography -- can't distinguish between slow-growing and aggressive ones.
Benefits and Risks of Mammograms
I talked about some of the other potential risks of mammograms including radiation exposure in a column last February titled "Deja Vue: Questions about the Timing Of Mammograms."
What about women with a strong family history of breast cancer or those who have inherited the BRCA 1 or BRCA 2 gene? The USPTF was clear to address only women at average risk for breast cancer and not those women at particularly high risk.
For high-risk women, an MRI scan of the breast for breast cancer screening is thought to be more sensitive than mammograms and therefore more likely to pick up subtle breast changes or early breast cancer and it is not associated with ionizing radiation.
But we still do not have enough research on screening MRIs in young high-risk women to know if they are safe, effective, and worth the greatly added cost (both in dollars and in needless biopsies, scares, missed work, etc.).
I suggest that until we learn more about the benefits and risks of MRIs, every woman at high risk should talk with her doctor about the pros and cons of all available tests, including routine mammogram, breast ultrasound and periodic breast MRI.Every woman's medical history and breast exam will be different and only when all aspects of a woman's history are taken into account can the best decision for screening be made. In the end, the decision should be made between a woman and her doctor.
In addition to a detailed conversation with your practitioner about the best way to be protected, all women should:
1) Be familiar with how your breasts feel and what is normal for you -- and do not hesitate to examine your breasts and to report any change or concerns to your practitioner
2) Continue to expect a regular breast examination by your practitioner, regardless of your risk factors.
3) Discuss the benefits and risks of routine mammograms with your practitioner if you are between the ages of 40 and 50.
4) Continue having a yearly mammogram starting at age 50.
Do New Guidelines Just Confuse Women?
I fear these new guidelines will do more to confuse rather than help women and will further dissuade them from getting the necessary screening tests they may need.
Unfortunately, with the current economic crisis, too many women are delaying routine preventive care and worse yet, delaying or avoiding more urgent care as well.
On the other hand, the new guidelines will perhaps lessen the load of many mammogram centers that are already overworked and overbooked. I know it takes patients up to six months or more to wait for a routine mammogram.
My biggest worry however is that insurance companies will not pay for routine mammograms in women under 50 and for women over 50 who make the informed decision to do so on an annual basis.These new guidelines do not persuade me. I plan to continue annual mammograms as I am over 50. I will also advise my friends and patients between the ages of 40 and 50 to consider continued breast exams and mammography, too, because they are still the best way we have to diagnose breast cancer early and potentially save lives.
What are your thoughts on screening? Are you under 50 and had breast cancer diagnosed by a routine mammogram? Have you had a false positive result? Are you worried about the cost of screening tests and whether your insurance will pay for them?
As always, I welcome your questions and comments.
Dr. Marie Savard is an ABC News medical contributor and author of "Ask Dr. Marie: Straight Talk and Reassuring Answers to Your Most Private Questions."
Return to News Home