The Smokescreen of Screening

In medical school I was taught that a screening test should have 3 characteristics. It should have a high sensitivity and specificity. It should be inexpensive. It should be low risk.

It gets considerably more complicated in the real world. The standard that has been most often applied has been cost per year of life saved. That theoretically takes all of the desired characteristics into account.

When the thought leaders in a field sit down to make recommendations they have to weed through immense amounts of data. It can come from studies of varying validity and biases.

In gastroenterology, colorectal cancer screening is a big part of the practice. Gastroenterologists also involve themselves in surveillance when higher risk people are identified.

There are other considerations as well. Let us be honest. If a group of gastroenterologists want to come up with colorectal cancer screening guidelines it is in their best business interests to recommend testing that will be to their financial benefit.

Political concerns also play a part. Katie Couric lit a fuse for the American College of Gastroenterology when her husband died of colon cancer. It quickly became an opportunity to make colonoscopy every 10 years for screening the standard of care.

Colonoscopy is the best screening test for colon cancer if done by qualified individuals. It is strongly supported by clinical research. It is supported by the drop in mortality since it became the standard. It is more cost-effective than mammography in breast cancer. Still, the long term trial to prove it absolutely saves lives is lacking.

The United States Preventive Services Task Force (USPSTF) looked at colorectal cancer screening last year. They did so right after a joint statement had been issued by a number of other organizations. Differences were present but the one that got the most attention was CT Colonography (Virtual Colonoscopy) not being endorsed.

That came as no surprise based on the medical literature. Some studies have shown the test can be highly sensitive and specific but others have not. It is also not cost effective unless patients with polyps less than 1 cm in size are not sent for colonoscopy.

One thing that gastroenterology has learned over the years as a field is that out screening and surveillance intervals are too short. Over the past 25 years the intervals to follow-up on pre-cancerous polyps (adenomas) have gone from yearly to up to 5 year intervals.

There is even a push now to treat a patient with a single diminutive adenoma the same as a patient with no polyps.

It can go the other way. Hyperplastic polyps were thought to not be a risk factor for cancer 15 years ago. Now, depending on size and location some of them (not all) have been found to be more dangerous than adenomas.

Increasing screening intervals can be difficult. It is hard to do a test every year and then start telling patients it will now be every 3 or 5 years. The data may support it but people will naturally feel as if they are putting themselves at risk.

Anchorage gastroenterologists all follow the screening guidelines. Unfortunately, there have been patients in my office from elsewhere who were told to have colonoscopies done well before the guidelines recommend. That is a tough discussion because most patients do not know who to trust and can remain skeptical even when they read the guidelines themselves.

Guidelines are just guidelines. Modifications can occur at times. There are findings that the guidelines do not take into account. Hence, there will be times when someone is told a shorter interval because of legitimate reasons.

The USPSTF just recently published new recommendations for breast cancer screening.

Breast cancer is a politically charged diagnosis. It has many advocates and it explains why diseases that kill far more people, including colorectal cancer, get less attention.

As soon as the recommendations were published it seemed like everybody was an expert on breast cancer. It become a battle cry for what we could expect under a new health care system.

The health care bills have major problems but this change in recommendations has nothing to do with reform. If you read through the rationale, it is easy to understand. All of the concepts mentioned above about how to measure screening tests were used.

The media has been full of examples of women who are alive today because they received a mammogram before age 50. There are plenty of people alive today because they had a colonoscopy done before age 50. Most of them had risk factors that led to the test being done and the USPSTF states cases can be individualized.

Why not screen everybody for everything starting at age 20? After all, that might save millions of lives worldwide. It is also cost prohibitive and has other downsides.

It is hard for a stupid stomach doctor to know whether the present USPSTF recommendations for breast cancer make sense. One thing that would be nice is more arguments against them being provided with excellent clinical scientific data. The recommendations appear to be scientifically defensible on inspection.

Change that appears to be taking something away is difficult to implement. It only gets worse with the legal and political climate in this country.

There is no way to stop all disease. The idea is to create a system where you identify the people at the highest risk and treat them appropriately. Sometimes people will not be caught in the net because the net is designed to catch most and not all cases.

Guidelines need to be based on data and the right decisions need to be made. It is what is right even if it is not what is always popular.