I can you my personal perspective on this process, as I did not match last year. On the advice of some very smart senior residents in Radiation Oncology, I decide to rank all of my prelim and transitional year programs after my Rad Onc programs so that I would have an internship position. The argument made by said residents was that you can always move to research fellowship after internship year and re-apply vs. going after a position that becomes available outside of the match.
This approach worked well for me for multiple reasons:
1) I aspire to stay in academics, so pursuing time in a research fellowship was a likely part of my long-term plan, be it before residency, during residency (i.e. research blocks vs. Holman pathway), or as a fellowship once residency was complete. So, one way or another, I knew there was likely going to be significant research time in my future. This point may not be the case for everyone, but it made it that much easier for me to digest the idea of finishing internship and then heading into the lab for 1-3 years.
2) It would make me eligible for PGY-2 spots coming open outside the match throughout the year. By my count, as of today (1/20/11) there have been no less than NINE POSITIONS available outside of ERAS. NINE! Some were made known nationally (i.e. on the ASTRO and SDN websites) and others were less public and more word of mouth. Regardless, the opportunities are not only for a spot, but for spots at good to great places! Just look at the last few here:
http://cs.astro.org/forums/default.aspx?GroupID=14
Cleveland Clinic, Emory, Maryland, etc
stellar opportunities! If you choose to not do your internship, these options are off the table. Furthermore, theres a very real possibility that even if you did your internship and nothing worked out during that year and you went on to pursue a research fellowship, you could jump ship during the research time and start a position immediately. Some of the spots on the ASTRO website went VERY quickly this year. Time is of the essence in applying for them if you take this approach. Apply early, often, and stay in touch with the programs. Phone calls to follow-up on making sure all of the materials were received have turned into interview opportunities. This is NOT the same game as the match, scores matter, but not nearly as much. Who you know matters much more, which brings me to my next point:
IF YOU DO NOT MATCH, STAY IN TOUCH WITH YOUR MENTORS/LOR Writers/Etc.
Ive hit some brick walls applying for spots outside of the match, and other times Ive had mentors willing to pick up the phone and the interview has followed that call pretty closely. Were talking r-squared value of >0.90.
I am an over-planner, so when I went into the match knowing the risk of not matching, I had arranged for meetings with potential research mentors and fellowship programs that gave me some comfort in knowing that it was highly likely I would have a position in research at the end of my internship, in a worse-case scenario. So, Plan B was all but set in stone before I finalized my rank list with prelims/TYs at the end behind the Rad Onc programs. This helped to make me comfortable with the possibility of only matching for the following year.
So, in summary, my n of 1 sample size speaks to the approach of doing your internship.
1) I think there is certainly some value in attempting to make sure its a prelim, if you are open to the idea of attempting to become a categorical medicine resident as one possible option for PGY-2 and PGY-3.
2) Stay in touch with mentors and letter writers. This field is small and someone with a good relationship and a reputation of moderate to significant prominence can do wonders for your opportunities.
3) Plan ahead. Have plans B, C, and D in place so that you have a job come July 1, 2011 AND July 1, 2012.
4) Dig deep in your core to see how badly you want to do Radiation Oncology. By my calculations there were anywhere between 40 and 60 unmatched applicants (taking all numbers into consideration) last year. For me, failing to match in no way deterred me from pursuing a career as a radiation oncologist. On the contrary, it made me even more resolute in achieving that goal.
I am happy to help further however possible, be it by PM or by replying to this thread. I hope this helps!