The three codes you listed are all for the highest level of complexity. If I had to guess (because you didn't list the denial reason), I'd imagine the payer wants to see some medical documentation to justify 77263 over, say, 77262. Particularly if you only bill the highest level for each service. It'd be like always billing 99215 for every office visit. Either the corporate payers changed their guidelines, or they're cracking down on potential fraud by requiring medical records.
I don't know your practice, perhaps you are only doing the most complex radiology procedures. However, I'd review the section of the CPT manual relating to these services to make sure you're meeting all documentation requirements. 77263 for instance requires custom shield blocks, three or more separate treatment areas, special beam considerations, tangental ports, or highly complex blocking in order to be justified (not all of those, but at least two are required). I'd be willing to bet that 77290 and 77334 have similar requirements.
One other thing, as I used to struggle with these sorts of denials everyday. Not every denial is exact and accurate. There should be a remark code attached to a denial, indicating what exactly is wrong with the claim. If there isn't, that's a whole other problem, but even if there is, the remark codes are generalized and do not necessarily cover every possible situation. Additionally, the people applying the remark codes are human, and errors occasionally happen. Review the remark code to ensure it isn't some simple problem. Once you're assured it isn't a keystroke error, you can go down the rabbithole of LCDs and coverage determinations.