I find it ridiculous that a full explanation of what screening means has not been a major part of the public conversation about the new recommendations for breast cancer screening by the U.S. Preventive Services Task Force (USPSTF). I wish to clarify this issue to allow for a more fruitful discussion about these, and other, medical recommendations..
Recently, I posted thoughts about, and a defense of, the USPSTF http://drmaliareckons.posterous.com/breast-cancer-screening-part-1-overview the group charged with evaluating medical research and evidence of benefit for a large variety of health services. The USPSFT makes recommendations, and regularly amends them as new information about services and relative effectiveness becomes available. In later posts I will consider the breast cancer screening recommendations more specifically and consider some common sense ways to understand them and other medical services.
The importance of screening is obvious as it is an integral part of primary care medicine. Yet the public has no perception of the significance or concomitant risks; and the popular media seems to have made no effort to explain it. The opportunity to do so has been available recently with a string of related news items. Besides the recent change in breast cancer recommendations, there was also a report in October that the American Cancer Society (ACS) may be changing its stance on "cancer screening." It was reported that the organization may start pointing to the fact that aggressive "screening," though it saves lives, may have been over-sold and, in actuality, the issue is more subtle and that testing can often lead to further evaluations and treatments that can have negative impact on life.
After being reported in the NYTimes http://www.nytimes.com/2009/10/21/health/21cancer.html the ACS website published a formal statement from its CEO, John Seffrin http://www.cancer.org/docroot/MED/content/MED_2_1x_A_Special_Message_from_CEO_John_Seffrin_PhD_on_Cancer_Screening.asp to try to clarify the perspective, a response which I actually feel only added to the general public's confusion, and muddied the water of later conversations.
Adding to the support for understanding the concept of screening is that on the heels of the new USPSTF recommendations about breast cancer screening was a change in the formal recommendation by the American College of Obstetricians and Gynecologists (ACOG) for pap smears and cervical cancer screening http://www.acog.org/departments/dept_notice.cfm?recno=20&bulletin=5021 which advised a later start of the testing and less frequent testing due to risks of problems after possible treatments and the limited benefit of doing pap smears more often.
Yet even with a string of headlines about changes to formal medical recommendations related to screening, I have seen essentially no effort to help the public understand the fundamental concept. And, considering the strong feelings and visceral emotions many people have expressed, this failure is very unfortunate. We physicians should feel an obligation to clarify this, post haste.
So let's get to it.
Screening tests look for important conditions before any problems / signs / symptoms become apparent.
Whether a screening test is "good" or not, and whether we should use time and energy for the test, is a judgment call that must consider a variety of factors related to the test and the medical condition being screened for. Let's consider some of these factors as well as how breast cancer screening relates.
- Screening tests are only meant for low risk patients.
I can think of no other point more important to understand related to screening for medical problems. In the last few weeks I have had multiple conversations with people, including some who work in health care; seen commentators on TV; and read newspaper and web-based articles which seemed to miss this point as they attacked the USPSTF's recent recommendations for breast cancer screening.
Low risk patients for breast cancer would be women with no first-degree relatives (mother, sister, daughter) or not more than one more-distant relatives (cousin, aunt, grandmother) with breast cancer, as well as no known high-risk breast cancer genetic markers. But, also, in considering risk for breast cancer, we also should think about use of estrogen-based birth control pills, age of first pregnancy and total time used for breast feeding.
Finally, if a finding is noted by the patient or a physician, the patient is no longer in the "screening pool." Rather, that person is being "evaluated," and not screened, for a problem.
The USPSTF recommendations are not meant for any women with suspicious findings on exam or with any increased risk for breast cancer. This is fundamentally important and can not be stated too strongly or too frequently.
- The condition being checked for must be relatively common.
If a condition is not relatively common, doing mass screening would mean we must test a huge number of patients, using massive resources, and not find many cases. Logic will dictate that we should not use our medical providers and resources looking for problems that are not common.
Breast cancer is certainly a frequent health problem with estimates that about 11% of all American women will be diagnosed in their life. But it is clearly occurs more frequently as women age with most cases in women over 50, and the highest rate of disease in women over 60. Though we often remember and discuss the women diagnosed at young age, that is much less common than breast cancer in older women.
- The condition must be significantly dangerous.
If we are screening, our goal is to offer patients more years of good health. If the diagnosis is not dangerous or the illness load is not great, our energies and resources will offer little "bang for the buck."
Breast cancer is a major killer for women. But, again, it kills many more older women than younger women. Some would say that the number of years saved when a younger woman is diagnosed with early screening makes that screening effort more valuable. But since screening is meant for whole populations we must consider the prior points and, since younger women have such a lower frequency of breast cancer, that the relative total burden saved by screening efforts is small compared to the effort of full screening.
Another unfortunate aspect of breast cancer, as well as other cancers, is that we often can not know how deadly a cancerous growth might have been if it were not removed. Evidence suggests that some cancers are more aggressive and others less. This means that when breast cancer screening uncovers a problem, a doctor can not tell a patient what the risks fully are. We are always working with incomplete information. At times, a more aggressive cancer may already have spread, while a less aggressive cancer may be far from metastasizing. Yet the formal medical recommendations may be the same for treatment options because we simply can not tell the difference.
- A screening test should uncover a problem "early" enough for treatment to prevent severe illness / death.
Some screening tests find pre-cancerous findings that allow for an early procedure that significantly lessens long term risk for the patient. These are optimal. Examples include Pap smears for cervical cancer and colonoscopies that allow for removal of pre-cancerous polyps from the large intestines.
Other screening tests only provide possible early detection, after actual cancer has begun. That is obviously less preferred. Breast cancer screening with mammograms fits that bill. It is the best we have, but it's not a great screening test. And, when seen in light of the last point that we do not always know what cancer lesions are more aggressive or less aggressive, we can see that it is not a great method to look for breast cancer, though it is our best weapon.
- A screening test should be relatively innocuous.
No test we recommend for a large number of patients on a regular basis should be exceedingly dangerous, painful, difficult to carry out or expensive. Otherwise, ultimately, patients would not want to have the tests done, we might be causing more health problems than we are preventing and the financial burden would be prohibitive for our whole system. Clearly, none of those results is acceptable.
Mammograms and related tests like ultrasound and MRI, along with clinical breast exam, are not comfortable according to many women, but they certainly are not, on their own, exceedingly painful, dangerous or difficult. In this regard the tests used for breast cancer screening are quite reasonable, even if, as noted above, they are not of the best quality for uncovering cancer.
- A screening test should make accurate diagnoses.
A test needs to be accurate. If a test seems to find a problem that is really benign ("false positive"), a patient too often will have unnecessary emotional stress and will go through testing that has additional risks. And, if a test appears benign when it actually misses a true condition ("false negative"), we are offering reassurance to a patient and failing the primary purpose of our efforts.
It is imperative that we only suggest patients undergo screening tests which are accurate and have as few false positives and false negatives as possible.
Regrettably, our breast cancer screening tests do have many false positives leading to a great deal more testing that ultimately proves unnecessary, especially in patients under 50 years of age, as well as too many false negatives because the technique of mammograms, basically looking for a slight variation of the shadow of x-ray images through breast tissue is very subtle and can miss early cancerous changes.
- Treatment options for a condition uncovered should be effective.
If a screening test does find a condition, it is only right that a reasonably effective treatment is available for the patient that can lessen suffering and improve life.
Some cancers simply do not have good treatments for when they are found. I think of pancreatic cancer which is very difficult to find early, thus is often found quite late, and most often requires a significant abdominal surgery.Other screening tests, such as Pap smears for cervical cancer, find pre-cancerous changes and allow for relatively easy treatment that prevents progression to full cancer.
Breast cancer, luckily, does have treatment options, including surgery, radiation and at times chemotherapy. Unfortunately, those treatments are at times inadequate as the screening tests find the cancers too late, or the cancers found are inherently aggressive and already have metastasized.
So there you have it. Screening, a fundamentally important practice in primary care medicine, needs to be better understood by the public. And I hope this primer helps in that effort.
I still plan for two more posts related to the recent change of the breast cancer screening recommendations and the hullaballoo it has triggered. Watch for them soon.
Timothy Malia, MD
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