I'm certainly not anything close to a "senior member", just a lowly PGY2, but here are my humble and mostly-uninformed recommendations on things to evaluate when you interview at a program, roughly in order of importance. This excludes location (i.e. how close you are to family, significant others, big cities, etc) because programs can't control these things.
1) "Fit": The fact is, radiation oncology is unlike a lot of other fields in that you will spend a lot of time in close proximity to your attendings and co-residents. Contrast this to IM (I did a prelim medicine year), where on a wards month, you might be with your staff from 8a - 2p, and free to work with your upper level resident the rest of the time. You need to feel like this is a place you can show up for work every day for four years and get along with your co-residents and attendings without significant personality differences. Admittedly, this is tough to feel out in a day, which is part of why I think a lot of people match where they did away rotations. In many ways, you're applying for an apprenticeship with lots of close feedback and life is better if you like the folks you see on a daily basis.
2) Outcomes: Dr. Terry Wall gives a talk at ARRO session which happens yearly on the Saturday before ASTRO. He shares advice by prior senior residents who are now working. One common theme I appreciated this year was that many people thought they would do academics or private practice, but ended up applying for both types of jobs. That being said, if you're dead-set on academics (or PP), it's helpful to know what types of jobs people have gotten in recent years. Most programs will discuss alumni; take note of where they ended up (both in terms of geography and job type).
3) Workload: Is there lots of scut (i.e. calling referring docs to ask for notes, uploading outside images to PACS, etc)? What is coverage like? If your co-resident is sick or on vacation, do you have to cover their staff for them? Again, this is hard to evaluate in a single interview day, and even more difficult to ask of the residents in the program where you're interviewing without sounding like a special snowflake. That being said, see if you can find out if there is good "front office support" for these sorts of things. You have other things to worry about, like consults, staging, contouring, prescriptions, managing toxicities, etc.
4) Technology: Everywhere has IMRT, SRS, SBRT, brachytherapy etc, but don't buy into the hype of "Protons in 2 years!" unless the digging has started. If you need protons in your training (hint: you probably don't), then be wary of these sorts of promises. Make sure the technology available will reflect what you want to do in the future.
4) Research time and opportunities: Do you want to do lots of research? Is research time guaranteed? If so, how much? How productive are residents? If your project requires more than the normally allotted time, will you get more time to work? If your project is short, will you be required to return to clinic? Do you want lots of research, or would you prefer more clinic time?
5) Didactics: There's a steep learning curve in RO, so it's helpful to have a structured, successful program to teach you rad bio, physics, and clinical topics. Ask the residents if there is protected teaching time, how they feel about their learning, and how much they have to rely on "self-directed" studying. Of course, you'll have to study on your own before boards, but it's nice to get a sense if academic time prior to PGY4 sets you up for success.
6) "Extras": Think moonlighting (allowed for everyone? case-by-case? forbidden?), vacation time, educational funds, personal workstations, conference attendance policies, ability to rotate at outside practice, cafeteria vouchers, etc. It's easy to think these things can be put off to the very end and won't impact your training, but some folks will really need moonlighting $$$ to support a family and/or live in pricey locales, and having a good financial support means you can go to nice conferences without going broke. Also, who doesn't like free food?
Of course, everyone will have different priorities, but this is kind of how I think about it after a few months on the job. That being said, I love where I work, but I certainly didn't appreciate all these factors when I was interviewing.
Best of luck!
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