Anytime ladyparts are in the news, it’s not long before there’s a palpable feeling that longstanding norms of gender equity have been violated and that balance needs to be restored. Often, this just means getting back to the really important stuff, like whether to invade Iran, Syria or both. But there’s also the point that men have parts too, and should have a share in the limelight, the same as women do when we discuss important stuff.
So, I thought I’d talk about a dangly dilemma faced by men of a certain age – whether to take the PSA test for prostate cancer.
These days a lot of authorities recommend against testing. I have ignored their advice, and get tested every couple of years (news good, so far!). So, who is right? And does the argument extend to other parts and tests?
update I thought I’d add a followup question here, rather than in comments. From a decision-theoretic viewpoint, the arguments against testing imply, for consistency, the following further recommendations (subject to some qualifications I’ll spell out).
*First, that someone who takes the test (ignoring the guidelines) and comes up with a high PSA score should not have a biopsy, and should not be tested again.
*Second, that someone who has a biopsy and gets a bad result should just ignore it, and not get tested again.
The qualification is that this treats the cost of the PSA test and the biopsy (which, as discussed in comments, carries some non-trivial risks) as small, relative to the benefits of even modest changes in treatment (such as a shift from complete ignorance to “watchful waiting”). Does anyone know whether these recommendations have in fact been made? If not, can anyone provide a defence of what seems to me to be an obvious inconsistency? End update
The PSA is a test with a low rate of false
positives negatives and a high rate of false negatives positives. So, if the test comes back negative, it’s unlikely that you actually have cancer. For me, that good news is certainly worth the cost to me (time and a bit of discomfort) of the test.
On the other hand, if the test comes back positive, there’s still a better-than-even chance that there’s no cancer. You can get a biopsy that gives a pretty accurate determination, and that’s what I would plan to do. Again, the value of the good news is worth more to me than the cost (more time and more pain).
The unpleasant decisions come after a positive biopsy. For those who haven’t read up on it, prostate cancer presents some pretty scary choices – untreated it leads to a painful death, while treatment is quite likely to stop your parts functioning properly in any capacity, and may not work anyway. On the other hand, lots of cancers are slow-growing and you may well die of old age before they cause any problems.
Based on that, my planned response to a positive biopsy would be to keep testing (it appears there’s some capacity to check how bad it’s getting) and change some plans that depend on life expectancy. I think the capacity to make plans outweighs the negative effects of learning the bad news.
So, if my analysis is right, I’m better off having taken the test whatever the outcome. For a decision theorist like me, that seems pretty clear cut.
What are the counter-arguments?
First up, I don’t pay the cost of the test (here in Australia, most things like that are free of charge). So, in terms of social costs and benefits, my analysis is incomplete. Still, I guess that the cost of my time and trouble is at least as much as the cost of doing the test, so the social cost is no more than double my private cost. Perhaps, if I were paying out of pocket I’d be tested a little bit less, but I don’t think that’s a big deal.
Second, some people might just prefer not to know. All I can say is that I’m not one of them – I feel more in control when I have information, even if I can’t really act on it.
Finally, and the most serious objection, maybe I won’t be able to stick to my plan of rejecting treatment if there’s a positive biopsy. In the decision theory business, we call this “dynamic inconsistency”. I hope I don’t have to find out about this, but for the moment I feel confident in my resolve.
I don’t know for sure how this translates, say, to mammograms. The official recommendations have been shifting against screening there too, raising the advised starting age from 40 to 50. But, as with PSA, it’s difficult to find a clear presentation of the reasoning behind the argument.
fn1. Logically, of course, “neither” is also an option. But let’s not be pedantic.
fn2. Irony alert off