Welcome to “From the Archives”, where I dig up old posts and see what’s changed in the years since I originally wrote them.
From time to time something fun reminds me of an old post of mine and I get all excited to go back and research what’s changed since I originally wrote them.
This is not one of those times.
A past post popped in to my head last week, but not for a good reason. A childhood friend of mine was diagnosed with ovarian cancer recently, which is a bit of a shock since she’s only 35, and hits close to home since she has a daughter just a bit younger than my son. Working at a cancer hospital I am unfortunately used to seeing early and unfair diagnoses, but it still has an extra sting when it’s someone you know and when they’re in the same phase of life you are. This friend actually has an interesting intersection with this blog, as she’s a science teacher whose class I’ve visited and given a version of my Intro to Internet Science talk to. She does great work with those kids, and I loved meeting her class. If you’re the prayers/good thoughts type, send some her way.
Not the happiest of introductions, but the whole experience did remind me about how important it is for people to know the signs of ovarian cancer, as it can be easily missed. Additionally, it made me think of my 2013 post “What Can Your Dentist Tell You About Your Risk For Ovarian Cancer?” where I blogged about the link between congenitally missing teeth and ovarian cancer. I wondered if there had been any updates since then, and it looks like there are! Both scientifically and with a couple dozen spammers who left comments on my original post. Cosmetic dentistry folks apparently have a lot of bots working for them. Anyway, let’s take a look! At the science, not the spammers that is.
First, some background: For those of you who didn’t read the original post, it covered a study that found that women who have ovarian cancer are 8 times more likely to have congenitally missing teeth than women who don’t have ovarian cancer. Since I have quite a few congenitally (ie born that way not knocked out or pulled) missing teeth (both mandibular second molars and both mandibular second bicuspids), I was pretty interested in this fact. I used it as a good example of a correlation/causation issue, because there is likely a hidden third variable (like a gene mutation) causing both the missing teeth and the cancer as opposed to one of those two things causing the other one.
So why missing teeth? Well, first, because it’s kind of fascinating to think of tooth abnormalities being linked to your cancer risk. Dental medicine tends to be pretty separate from other types of medicine, so exploring possible overlaps feels pretty novel. When someone has teeth that fail to develop (also known as hypodontia or angenesis), it’s thought to be a sign of either an early developmental interruption or a gene mutation. Missing teeth are an intriguing disease marker because they are normally spotted early and conclusively. Knowing up front that you are at a higher risk for certain types of cancer could help guide screening guidelines for years.
So what’s the deal with the ovarian cancer link? Well, it’s been noted for a while that women are more likely to have hypodontia then men. Since hypodontia is likely caused by some sort of genetic mutation or disruption in development, it made a certain amount of sense to see if it was linked with cancer specific to women. The initial study linking missing teeth and ovarian cancer showed women with ovarian cancer were 8 times as likely to have missing teeth, but subsequent studies were less certain. A 2016 meta-analysis showed that overall it appears about 20% of ovarian cancer patients have evidence of hypodontia, as opposed to the general population rate of 2-11%. Unfortunately there’s still not a definitive biological mechanism (ie a gene that clearly drives both), and there’s not enough data to say how predictive missing teeth are (ie what my risk as a healthy person with known hypodontia is). We also don’t know if more missing teeth means greater risk, or if it’s only certain teeth that prove the risk. So while we’re part way there, we’re missing a few steps in the proving causality chain.
Are there links to other cancers here too? Why yes! This paper from 2013 reviewed the literature and discovered that all craniofacial abnormalities (congenitally missing teeth, cleft palate, etc) seem to be associated with a higher family cancer risk. That paper actually interviewed people about all their family members cancer histories, to cast a wider net for genetic mutations. Interestingly, the sex-linked cancers (prostate, breast, cervical and ovarian) were significantly associated with missing teeth, as was brain cancer. In some families it looks like there is a link to colorectal cancer, but this doesn’t appear to be broadly true.
So where does this leave us? While the evidence isn’t yet completely clear, it does appear that people who are missing teeth should be on a slightly higher alert for signs of ovarian or prostate cancer. Additionally, I’ve sent my dentist and my PCP the literature to review, since neither of them had ever heard of this link. Both found it noteworthy. It’s probably not worth losing sleep over, since we don’t know what the absolute increase is at this point. However, it’s good to keep in the back of your mind. Early detection saves lives.