The Patient Equation

9The Steam Table

It may not be since high school physics that you've seen a steam table (see Figure 9.1), a chart of the pressures and temperatures at which water turns from liquid into gas.

If you plot these numbers on a graph, you get a view of where you are in the world, based on these pressure and temperature variables, a point that tells you, with definitiveness, whether water will be water, ice, or vapor (see Figure 9.2). You know, because you have all the information you need for the equation.

Perhaps you see where this is going. In a mathematically-idealized world, we would build that “steam table” for every condition, every disease—so that you would know who to treat, who not to treat, and what we should be treating them with based on empirical results. Using the example of PSA, prostate cancer, and radical prostatectomy—the surgical removal of the prostate—the columns of our steam table could chart PSA results, the rows could chart the patient's age, and in each box we would look at the ratio of the number of people who didn't suffer from prostate cancer versus those who did, after their prostates were or were not removed.

Figure 9.1 A steam table

Steam tables show the amount of a substance—typically water, hence the name—that is vapor versus liquid at a given set of combinations of temperature and pressure.

Figure 9.2 Phase diagram

Phase diagrams graphically ...