A brief comment...
I don't think it is helpful (in terms of getting into the field) to have "done research" if no publication resulted. Why?
Publishing shows that something can be started and finished.
In addition, the philosophic ideal of research is to share the findings so that the rest of the world can benefit, and so that others don't repeat the work.
Sadly, a lot of young researchers are victims of circumstance, such as the person whose PI was indicted (ouch). In addition, a lot of Junior faculty may steal rightful authorships from young researchers, a painful lesson most of us involved in research learn early on. Unfortunately, this falls into the "life isn't fair" category and nobody wants to hear reasons or excuses on the interview trail why something didn't get published, even though those reasons may be very valid.
The truth is, the majority of people getting interviewed these days have at least 1 published paper, or a few published abstracts. I think that medical students who want to get into radiation oncology should have a very frank discussion with their research mentors early-on. They should state that they are seeking "doable" projects that can result in published work in a time frame compatible with the application process (this usually means making connections early in the 2nd year of medical school). Potential authorship has to be hammered out at the initiation of the project. Discussing potential authorship may feel awkward and disingenuous (to the newbie) before any work has been done, but after having and observing these conversations multiple times, I can tell you that they are really no big deal and greatly clarify things.
If you have the luxury and time to do radiation oncology research, the more senior residents are very good at counselling med students which faculty members can give students "doable" projects, and who is generally supportive. They are an excellent information resource that should be tapped by students who find themselves saying "Crap, here I am a second [or third] year medical student, and I just realized I want to be a radiation oncologist I know I need some research, where do I start?"
But make no mistake about it, the publication matters.