In short, no, you shouldn't be concerned.
The radiation dose is very tolerable, and with sufficient pause in between (at 60 flights per year you have on the average 6 days, which is plenty) it's neglegible.
Sure, you may get cancer (nobody can guarantee you won't!), but if you do, you can't blame your travels for it. In all likelihood you would have gotten it anyway, and nobody will be able to tell why. May as well be from the water you drank or cancerogens in your food, or certain virus, or just... bad luck.
Radiation is a naturally occurring phenomenon, and the dose you worry about is way less than what flight crew tolerates easily and without any health issues. The unavoidable constant background radiation, while significantly lower, is probably just as harmful as the intermittent slightly higher exposure. Living in a concrete building is much more harmful (and no one worries about that, me included!), as the higher-than-average radiation is permanently present, not intermittent.
Even at the much higher doses that flight crew is exposed to (dozens of times more, over decades) your body is perfectly able to repair the damage, provided that there are rest periods in between (at least a day). Nature (or evolution, call it what you will) has -- within limits -- adapted to, and can cope with radiation and its damaging effects. DNA repair is a fundamentally important part of life. You couldn't ever go out in the sun, if it didn't work (at least, for the most part) reliably.
In radiotherapy, you get two-digit Grays over a couple of weeks (which, depending on tissue, corresponds to single-digit, double-digit, or triple-digit Sieverts). Not milli, not micro. So basically around ten million times the dose you worry about.
While such a huge dose doesn't truly go down "no effect" on surrounding tissue, even at these massively harmful doses the effects are surprisingly mild provided that there's sufficient rest periods between exposures. This is the entire point of radiotherapy. Healthy tissue will regenerate damage during the rest period whereas tumor won't.