He's making the fundamental error that all doctors who believe themselves able researchers do. He hasn't noted that in the UK, people who have previously suffered from cancer are specifically targeted by the NHS to receive vaccinations. So as a demographic they are MUCH more likely to have had all the boosters. So I think we can explain THAT correlation.
And people who have survived one cancer are at an increased risk of developing other cancers. That's hardly a new finding.
He hasn't, to my knowledge, published ANY paper on his opinion - I don't say hypothesis since I've just explained the correlation.
Now a study would specifically segregate patients based on how many vaccinations they have had. I'm fairly sure their will still be enough cancer patients who are unvaccinated, only has one booster and so on. That done, you have removed one bias. I can find no mention of any effort to do so.
But a proper study would require one to take a very large sample of people over 20 or 30 years to see if covid vaccination increases the statistical likelihood of those people suffering from cancer at some point. What he fails to point out is that an oncologist will have no reason to deal with a patient who doesn't have cancer. So he doesn't have an unbiased data-set.
It's a bit like me using the above as 'proof' that covid vaccines actually cure cancer.
I've seen videos by that guy before and to quote my favourite review 'he makes a grain of sand cover a desert of lies'.
Quoting the OPINION of an oncologist is technically termed here say.