The only twaddle worse than doctors talking about aviation is pilots talking about medicine
Radiation is dangerous. Therapeutic and diagnostic X rays kill 60000 patients a year in the USA alone. However it is both dose and duration dependant. The amount of radiation received in commercial aircraft by crew working usual shifts falls Within the level that has been deemed safe for those of us who work with radiation in medicine. We wear exposure badges and have been universally monitored for 40 years so the statistics are fairly sound. I receive far more radiation from one operation than crew will receive in a month
Sadly whether the dose is over 5 minutes or 8 hours is irrelevant.
If you have had cancer you will not get a new cancer from these exposures. Depending on the tumour your immunity and the risk of further malignancies may be increased whatever your occupation and you also run the risk of relapsing but you won't die from being a trolley dolly