When is a life-threatening disease not worth treating? When something else will kill you first.
This week, the U.S. Preventive Services Task Force issued new guidelines for prostate cancer screening . The New York Times explains :
Prostate cancer often progresses very slowly, and a large number of these cancers discovered through screening will probably never cause symptoms during the patient’s lifetime … Past task force guidelines noted there was no benefit to prostate cancer screening in men with less than 10 years left to live. … The new guidelines take a more definitive stand, however, stating that the age of 75 is clearly the point at which screening is no longer appropriate.
Well, sort of. The new guidelines do draw the line at 75. But the rationale hasn’t really changed. Here’s the key paragraph from the report:
In men age 75 years or older, the USPSTF found no direct evidence of benefits of prostate cancer screening. However, the USPSTF was able to establish an upper bound for the potential magnitude of the benefit of treating screening-detected prostate cancer in this age group, by extrapolating from evidence of treatment for clinically detected prostate cancer in this age group. For a population of men with an average life expectancy of 10 years or fewer, the USPSTF determined that the benefits of prostate cancer screening and treatment would range from small to none.
In other words, men 75 years or older aren’t worth screening because their life expectancy is 10 years or less. This matches the logic of the previous guidelines (“Older men … who have a life expectancy of fewer than 10 years are unlikely to benefit”) and, as the report notes, similar guidelines issued by professional medical associations. It also matches a study , cited in the key paragraph, that compared “radical prostatectomy” to “watchful waiting” in two groups of men. The study found that with prostate removal, “The absolute reduction in the risk of death after 10 years is small.”
More to the point, the 75-10 equation matches current U.S. life expectancy tables. The guidelines clearly identify life expectancy as a key factor in setting limits to screening:
The USPSTF found convincing evidence that treatment for prostate cancer detected by screening causes moderate-to-substantial harms, such as erectile dysfunction, urinary incontinence, bowel dysfunction, and death. These harms are especially important because some men with prostate cancer who are treated would never have developed symptoms related to cancer during their lifetime.
According to the latest U.S. government data, remaining life expectancy for a 75-year-old man is 10.8 years . But that number applies only to the most recent year on the table, 2005. If you scan up the column of numbers, looking back in time, you’ll see that remaining life expectancy for men at 75 has been edging up. Since 1980, it has increased by two years. And if you look at tables going further back, you’ll see that a 75-year-old man today can expect as much remaining life as a 70-year old man could expect in 1975.
In other words, life expectancy is increasing, and as it does, the age at which slow diseases are worth testing and treating also increases. Three decades ago, by the logic of the 10-year limit, a 70-year-old man wasn’t worth screening for prostate cancer. Today, he is. We have extended his remaining life to the point at which prostate cancer would shorten it. By preventing and treating other diseases, we have made this one worth preventing and treating, too.
So don’t count on the screening line to hold at 75. Over the next few decades, it could easily rise to 80.
One way to look at this trend is that the job never ends. The more we accomplish, the more work we have to do. It’s exhausting. Maybe we should back off and respect nature’s limits.
The other perspective is that there’s nothing more liberating – nothing more human – than shattering old expectations. This boring little tweak in the recommendations for prostate cancer is actually this week’s episode of the biggest story in the universe: biological emancipation. In the beginning, we accept a cause of death as nature’s course. Then we call it a disease and study it. Then we push life expectancy to the point at which the disease is worth treating. The truest measure of progress isn’t what we achieve. It’s what we undertake.
