I think any research helps. I did my research in biochemcial
enginnering. Not related to rad/onc, or even medicine in
general. What it shows, is ability to define a problem, look
into it, and solve it, then communicate your solution to others.
The research process is more important than the specific research
problem. Those that can do research, can do it in most any
field, those that can't won't ever be able. It seems to be an
innate talent. Looking at the big picture and then drawing
logical conclusions about what is next and knowing where to
go from there. Some people flounder as to what to do, some
people flourish with the possibilities. Everybody has their
talents, look deep into yours and decide accordingly.