I'm in touch with the author at the moment. His stat isn't wrong in an academic sense - if you look at CML cases over a long period of time, it's true. If you look at cases in a more recent era it's of course different.
I'm trying to find him a more recent, and thus more forward looking statistic.
The source he used was a very reasonable one - https://www.nhs.uk/conditions/chronic-myeloid-leukaemia/ - but I suspect it is based on stats from a study pre-2000 (ish).
Update: I gave him some more modern stats from a few sources, and he's going to change the article. It comes too late for the print edition, but the online copy will be updated. That's more important anyway, as it's the one someone who is diagnosed in the future might read followign diagnosis.
Update 2: The article now states very reasonably:
It develops more slowly than acute myeloid leukaemia, but it is similarly serious. NHS figures state that 30 per cent of men and 25 per cent of women die within five years of diagnosis, although recently developed drugs, according to research, have raised the five-year survival rate to 90 per cent or more.