by S. Todd Stolp MD
©December 2007
It is not necessary to have mechanical expertise in order to know that different models of cars are known for certain strengths and weaknesses. Volkswagen transmissions are famous for being nearly indestructible, but their electrical systems have a reputation for leaving one in the dark. Certain SUVs have had a nasty habit of tipping over, while some trucks are reportedly stout enough to haul a brontosaurus. Some engines require an oil change every 3,000 miles, while others may go 8,000 or more. In fact, if you have ever listened to the “Car Talk” radio show, it is astonishing how the skills that are desirable to find in an automotive mechanic are identical to the skills one would like to find in one’s personal physician. Perhaps the most artful component of both professions is the ability to identify those maladies to which one is particularly susceptible, and to provide a little preventive care before one finds oneself at the side of the road calling a tow truck.
Screening for cancer follows this principle exactly. When we are born we are dealt a hand of cards made up of approximately 30,000 genes. Each of these genes describe our hereditary characteristics, including our strengths and our susceptibilities to various illnesses and cancers. Some families have higher risks of breast cancer, some higher risks of colon cancer, some leukemia (cancer of the white blood cells) etc… In fact, with the recent surge in our understanding of human genetics, it is conceivable that in the future there will be a panel of blood tests through which health care providers will be able to predict which cancers and health conditions pose the greatest threat to individual patients. It may be that the schedule of recommendations for preventive health care – mammograms, cholesterol levels, blood tests for prostate cancer, special X-rays studies, etc… – will be personalized to each individual to provide the greatest benefit for the least expense.
But, of course, this only represents part of the story. While genes can predict certain risks we face, how we live our lives has an enormous impact on whether those potential risks become reality. To go back to our automobile metaphor, you may have a very dependable car, but if you drive it like a maniac you can bet that your brakes are not going to last and your engine life will fall short of expectations. Similarly, a smoker is exposing lung cells to an irritant which is encouraging cells to constantly heal, or reproduce. Over time, the particular lung cells that are best equipped to confront the challenge of tobacco smoke are those cells which are reproducing most rapidly. This environmental pressure is all that is needed to encourage a genetic weakness for cancer to surface. After all, cancer is simply a cell which has forgotten to do it’s job, and instead devotes all of it’s energy to reproduction. If the cards contain a susceptibility to allowing cells to behave in this way, cancer is the result of constant exposure to tobacco smoke.
It is the job of a health care provider to advise patients to undergo certain tests based upon their hereditary risks and personal behaviors. Standard recommendations for preventive health care are based upon the frequency of certain health conditions in the entire population. The United States Preventive Services Task Force (USPSTF) is the group assigned with the responsibility of developing these standard recommendations to prevent cancers from developing and to catch them at a stage during which cancers can be cured. In order to make such recommendations, the costs of screening tests – both monetary costs and physical costs – are taken into account. In addition, the USPSTF considers other factors before making recommendations, such as the accuracy of any given test, and the ability to alter the course of a given illness after a test result is abnormal. You can look up these recommendations at www.ahrq.gov/clinic/uspstfix.htm
While we do not come with a factory warranty, there are steps that can be taken to extend our individual mileage. It is worthwhile to consider the risks that are inherent in our families and to discuss preventive health care recommendations with our personal health care providers in order to maximize our ability to enjoy the ride.