The "cyclical" argument does not apply to rad onc IMO. Rad onc has always been non-competitive, with one exception-the IMRT era. In fact, it got so bad that to temporarily fix things (common theme in RO), they decided to extend residency training. All this did was it put a temporary band-aid on the problem.
I said one exception. I would posit that IMRT was such an innovative contribution to the field, that it turned a non-competitive field into a competitive one-albiet, temporarily. In fact, I would posit that the advent of IMRT is responsible for the bubble that was RO 5-10 years ago-the likes of which we are paying for now. IMRT not only made academic centers richer, it made the professional side of RO poorer-prior to IMRT professional fees were higher than technical fees for a treatment course (for the most part) because, naturally, more professional effort was involved in cutting blocks, shaping fields, etc-more manual labor was involved. With the coming of IMRT, technical side went up and professional side went down. While this was a blessing for academic centers, it was terrible for individual rad oncs -with one exception, people who owned their machines. Let's think about this for a second. Residency expansion only started after IMRT. Why is that? Because IMRT allows the residents to do many more minor things (contour, write notes, etc) and an attending to treat more patients for the institution. It also took the specialty from the practitioner to the institution.
People who owned machines benefited temporarily because academic centers started massive marketing. In addition, reimbursement was higher for the same services when delivered at academic centers-even if the only thing connecting the satellite to the academic center is a sign.
So really, it's not cyclical. RO was always on a decline. The increase in competition was a minor bump on the downward slope. A bump that can be attributed to two temporary things: 1) extending training by one year and 2) IMRT.
These two things will not happen again. Odds of them extending residency by another year are practically nil and last I checked, there isn't anything remotely close to IMRT-despite what is being promoted (protons, flash, blah, blah, blah). In fact, not only would I argue that rad onc was never in a "cyclical state," but has always been on a decline, I will argue that rad onc will follow nuclear medicine and this will happen over the next 10-15 years or so. If you don't know what happened to nuclear medicine, take a look at their message boards. I don't see why RO is any stronger than that specialty.
My 0.02