Humans are highly prone to overestimating the likelihood of rare events, such as shark attacks or winning the lottery. This tendency is known as “availability bias,” the inclination to judge the frequency of an event by how easy it is to recall examples from memory.
For example, if you’ve watched the movie “Jaws” or daydreamed what you would do with the Powerball jackpot, it will be quite easy for you to pull up vivid, emotional images of these events, making these rare events seem much more likely to happen.
The availability of these events in your mind overpowers the much more mundane reality that you actually have only 1 in 292,201,338 chance of winning Powerball. And even among beachgoers, the chance of being attacked by a shark is only about 1 in 11.5 million.
Now a new study, published in the Journal of Women’s Health, reveals that availability bias may also influence how often a doctor recommends cancer screenings for patients.
Overall, screening guidelines are designed to do the most good while causing the least harm. In the case of cancer, this means screening the patients who have the greatest chance of hiding a dangerous cancer at a treatable stage.
Screening routinely saves the lives of high-risk patients. But for low-risk patients, the cost and chance that false-positive results will lead to anxiety and even unnecessary treatments outweigh the very small chance of detecting a dangerous, treatable cancer.
In other words, for a population of low-risk patients, the harm outweighs the good.
Survey results from 497 primary care physicians show that doctors who have had cancer themselves, or experienced cancer with a family member, close friend, or coworker, are 17 percent more likely than those without personal cancer experience to act against established guidelines to recommend that low-risk women receive ovarian cancer screening.
“Most doctors are pretty comfortable with the idea that our personal experience can make a positive impact on our practice — we’ve known someone and so it gives us insight into how to take care of patients in similar circumstances,” said Margaret Ragland, M.D., pulmonary critical care specialist at UCHealth University of Colorado Hospital (UCH).
“This study helps us realize that sometimes it can go beyond that. Personal experiences can impact our practice in a variety of ways,” she said.
“Some people may think, what’s the harm in doing testing that’s not indicated? I’m going to get a negative test and it’ll make my patient feel better. But if you find something, it can lead to further follow up, causing complications, cost, and anxiety.”
This is why screening for ovarian cancer is not recommended for women of average risk. And yet when presented with an account describing a woman of average risk, 31.8 percent of primary care doctors who had personal experience of cancer chose to offer this screening. In comparison, only 14 percent of doctors without personal experience of cancer opted for patient screening.
The survey collected responses from 3,200 randomly sampled physicians who provide primary care to women. The primary goal of the study was to discover the characteristics of providers who might be at the greatest risk of recommending care that conflicts with guidelines. The researchers hope to identify and educate these potentially non-compliant doctors to help ensure that patients more uniformly receive the best possible care.
“The reasons that doctors with personal cancer experience may be more likely to not follow screening guidelines are complicated and we don’t know all the answers,” Ragland said. “But my hypothesis is that a doctor’s personal experience may influence their assessment of risk. You see a patient in front of you and you may assess the risk to be higher than it actually is.”
“We’re physicians, but we also have life experiences,” she said. “What this study tells us is that in ways we may not be aware, for better and for worse, our personal experience may affect our practice.”
The survey was funded by the Centers for Disease Control (CDC) and managed by study senior author Laura-Mae Baldwin, M.D., University of Washington professor of Family Medicine.