Your Medical Mind_ How to Decide What Is Right for You - Jerome Groopman [40]
“I read more and learned that even with proton beam, problems can creep up over time, like bowel incontinence and impotence, just like with standard radiation treatment,” he said. “I didn’t want to take the chance of later damage, although I did like the idea of a nonsurgical procedure.”
Matt said that, without exaggeration, he spoke with more than twenty different physicians expert in the field of prostate cancer. He was determined to find that subtle difference, to identify the advantage for him that must exist in one of the treatments at a certain medical center or with a specific doctor or technology.
But he was beginning to tire in his search. “I figured by then if I went to a surgeon, he was going to cut. If I went to a radiation specialist, he was going to radiate. And each specialist recommended their own way of doing it and gave me these statistics. But the numbers were not helping me.”
Would Bernoulli’s formula, multiplying the probability of an outcome by its utility, give Matt the numbers he sought to make a rational decision? Let’s assume that surgery and radiation give a roughly equal chance of cure. Given that assumption, we need consider only the side effects. We need to know the probability of each side effect for each treatment and the impact (in numerical form) it would have on Matt’s life. First, we would do the calculation for surgery, and then we would repeat the calculation for radiation treatment. The most rational choice for Matt would be the treatment that provides the highest expected utility. This would be the treatment that avoids the worst side effects and has the least negative impact on his life.
Alan Schwartz and George Bergus, professors at the University of Illinois and University of Iowa, respectively, vividly illustrate the daunting challenge of doing this calculation in their primer Medical Decision Making. They use as an example an informed consent document given to men considering prostate surgery. The document lists eleven different potential adverse outcomes, including common ones like erectile dysfunction and incontinence with leakage of urine, as well as less common ones like clots in the legs after surgery, infections, the need for repeat operations, and so on. The list of eleven outcomes doesn’t even include the potential risks of anesthesia. Schwartz and Bergus calculated that for these eleven potential side effects, there are over two thousand combinations. The next step is to imagine the quality of your life with each of these two thousand combinations of side effects and assign a number for each.
Recognizing how overwhelming this prospect is, some experts suggest that patients should focus only on the most frequent adverse outcomes. But even by winnowing the list of major side effects of prostate surgery to urinary incontinence and sexual impotence, the patient is still at a loss to assess the impact, since there is a great deal of variability in terms of the severity and duration of each negative outcome. Do you dribble urine only occasionally or do you consistently wet your underwear? Do you have a partial erection or no erection? Is your erection improved with Viagra? And if improved, is it enough for gratifying sexual relations? Or is lovemaking marred by anxious disappointment? Do these side effects last for months, or years, or are they permanent?
For a moment, let’s put aside these complexities and see how researchers have devised ways to come up with a number for the “utility” or impact of living with a side effect. One method is a rating scale. Matt would be given a straight line where 0 represents death and 100 represents perfect health. Then he would be asked to designate where being impotent would fall on that