That depends. Flight crew (pilots and cabin crew) do receive significant radiation. They are a great set to study as they are generally much younger and healthier than the average medical imaging and/or oncology patient.
Indeed, they're a very interesting exception to the general rule about healthy people not getting significant irradiation. Pilots in particular could be a useful group to study given that they have mandatory medical checks; however, I'm not sure that the sample would be large enough to yield any statistically significant results, even if the privacy issues could be circumvented.
(Also, you run into socioeconomic confounders: Can you find another population which has both the same irregular schedules and the wage scales of pilots?)
(Also, you run into socioeconomic confounders: Can you find another population which has both the same irregular schedules and the wage scales of pilots?)