A question that crops up again and again is how many people with Li Fraumeni Syndrome (LFS) are there in the UK? While it’s an easy question to ask, it’s not so easy to find an answer. The fact is that nobody knows for sure but we can make some educated guesses based on estimates of how often TP53 mutations occur. In the past I have used a figure for the UK of 1/10000 to 1/25000, which gives a theoretical count of mutation carriers in the range 6400 – 2560. That’s an awful lot of people when you think about it. And of course it does not include the 30% or so of people with LFS or Li Fraumeni-like (LFL) Syndrome who do not have a TP53 mutation.
I got slightly different estimates from a couple of the UK’s leading LFS experts. One suggested the rate of mutation carriers could be in the range 1/5000 to 1/20000, which means a population of carriers of between 12800 to 3200. Another very experienced clinician estimated 1/5000 to 1/10000, giving a UK population of 12800 to 6400. If we took a simple average of those numbers we’d come up with around 4300 in the population, add to that those without a mutation and you could easily have 5500 people in the UK who have LFS.
Of course when we’re asking the ‘how many people’ question what we’re often interested in is how many people are actually diagnosed? That is how many have been tested and formally diagnosed as having LFS or LFL? Again, nobody knows for sure. According to one of our experts the number could well be around 400 – 500. Our other expert suggested that only about 10% of people with LFS are formally diagnosed. Around 90% of those who have the condition don’t know about it. That’s an awful lot of people suffering early onset or repeat cancers, often with dire family histories, and not knowing why.