There is a well written article on NYT regarding mammogram screening that I want everyone in the world to read. The author describes the underlying motivation of that poor panel, much excoriated at this point: that statistically, financially, and for the women in question – physically, emotionally – it just doesn’t make sense to screen before age 50.
I’ve tried explaining this to a number of my friends, often to no avail – it’s a tough subject. The author points out the fact that understanding very large and very small numbers, and even more so, very large and very small probabilities, is not intuitive for many people. Because it is intuitive to me, and also because I have spent the last several years learning to understand those ideas, I have a hard time explaining it to them.
Without even considering the negative effects of frequent and unnecessary exposure to radiation from mammograms (which is a very interesting part of this problem to me), it’s simply not worth it. There are too many false positives, false negatives – reading the article for the discussion of these concepts alone is worth clicking over. Can you imagine the emotional and physical toll of being diagnosed and treated for breast cancer, only to find out you don’t have it?
The problem is more easily explained with colon cancer screening, I’ve found. Colonoscopies are uncomfortable, embarrassing, and risky. Perforation of the colon occurs at a rate of about 1 in 1400 to 1 in 1000 – that is, for every 1400 (or less!) people who get a colonoscopy, a hole gets ripped in one of their colons (source below). This requires surgery, with its inherent risks – you know how you sign a piece of paper that says you could die every time a scalpel or anesthesia is involved? Yeah.
So the fact that colonoscopies are recommended for everyone over the age of 50? A little scary. I would wager that I know at least 500 people in that age group, professionally or personally. That number will obviously go up as I get older. And as you are to get one per year? God, I’m getting scared just thinking about it. But, 1 in 1000 is considered a low risk – that’s only 0.1%. It all depends on how it is presented – I interpret the latter as less risky, intuitively, than the former.
Back to mammograms. It’s tough to say whether I will follow the new screening advice (you know, if it hasn’t changed in 15 – 25 years when it becomes more relevant to me). It’s hard to weigh the more nebulous risks of exposure to an invisible mutagen, and the possibility of unnecessary treatment against the more tangible (and publicized) demon – breast cancer. It’s hard for me – for us – to consider “invisible” risks (things that will happen so far in the future that they seem disconnected from their stimuli) in a rational way.
What do you think? Will you get mammograms before age 50 if you are asymptomatic?
Panteris, et al. 2009. Colonoscopy perforation rate, mechanisms and outcome: from diagnostic to therapeutic colonoscopy. Endoscopy 41, 941 – 951.