It is very clear to me that many of our foundational truths about preventative medicine is changing. And I’m not talking about the health care reform bill. I am speaking about the benefits and harms of screening tests.
For years, patients and physicians have understood that preventative medicine, which includes cancer screening saves lives. Celebrities, politicians, the media, advocacy groups and even US postal service stamps have embraced the notion that screening was not just a decision, but morally imperative.
But now, we are starting to question this simple message about cancer screening. “Take the test not the chance.”
Screening is not simply about benefits. There are some trade-offs involved. An example of this is demonstrated in the new guidelines for breast cancer screening set forth by the US Preventative Services Task Force in which mammograms are recommended less frequently. This is due to the high rate of false positive results and unnecessary over treatment causing much frustration and anxiety, especially in women under age 40 (Mammogram Guidelines Under Debate, Nov. 22, 2009).
The same holds true for prostate screening and the prostate specific antigen tests (PSA). This test may tell us more about inflammation then about cancer itself. The decline in prostate cancer-related mortality may not be attributable to screening but rather to aggressive new treatments. In other words, we are finding cancers that may never threaten a person’s survival and would otherwise undergo spontaneous remission before becoming clinical disease. The reality is that prostate cancer as well as breast cancer is a disease of aging.
The bottom line is that we have screening tests that are modestly accurate that may or may not make a real difference. And a normal value gives us false comfort that we do not harbor prostate cancer or breast cancer in our bodies, when in fact that may not be the case — especially as we get older.
We clearly need to develop predictive markers to determine which cancer cells will regress and which will be more aggressive. This may not be far from the future considering there is a biochemical marker currently being tested to help predict which colon cancers are more aggressive and likely to spread to other parts of the body. Differentiating low and high risk cancers will provide useful tools to guide physicians and patients in informed decision making in determining which patients need a minimalist approach and which individuals require a more aggressive treatment plan.
Until that time comes, discuss the pros and cons with your clinician and make a screening choice based on individual need and what’s best for you.