I am well aware of hitting 240+ on Step 1 and doing well in school. As for research, I am currently in a lab conducting basic/translational research on solid tumor metastases. I have talked to the PI and we can see (with a lot of hard work of course) 2-5 papers (hopefully a few of those would be first author) in the four years. In addition, I hope to complete some clinical (more heme-onc related) research and case reports during my times in the school during MS3 and 4 years. For my situation, does this sound like a good plan if I apply RadOnc in the future? How much will little or no RadOnc hurt me in this case? Of course, I will try my best to get RadOnc research done during my away rotations and over this summer.
Man... if you get 240+ Step 1, do well in medical school, and crank out 2-5 publications in the basic/translational cancer research sciences (of which a few are first author), and complete some clinical research/case reports... all before you send out your ERAS application during the beginning of your fourth year of medical school without taking any time off in between... then you are a F***ing rockstar!!!
Not to say it is impossible... but as someone who completed a PhD in cancer/radiation related basic science research I know that many of my fellow students will barely be able to complete 2 first author publications in the basic sciences with four full years of dedicated research in the lab in addition to four years of medical school. Again, not to say that you should not go for it or that no one has done it before... just realize it is a lofty goal for the basic sciences (at least from the molecular side of cancer research; I have seen these many pubs in a short period of time from people doing bioinformatics, however).
One thing I could suggest it to submit an abstract to the annual ASTRO meeting by December of your MS3. ASTRO abstracts are published in the Red Journal so while they may not be a manuscript publication they do show up in the publication section of your ERAS app and it will look good as you are already participating in the field's largest meeting. I will admit that ASTRO is not the best meeting overall for a student presenting basic science research, since basic science is not a big highlight of the meeting... but if it is reasonable data for cancer it would be highly likely to be accepted.
Just be sure NOT to hurt your Step 1 score or other performance by taking too much time away from medical school for research! Basic science takes a very focused effort so if you want to accomplish something along the lines you are suggesting you should seriously consider taking a year off for research. The NIH has a pretty well known HHMI research intern year program I know a few students have done. That is the only program off the top of my head but I'm sure there are more out there. I know that the idea of lengthening an already long process is nauseating but it is only one year in the grand scheme of things. Either way... if you intend to have a publication for your ERAS it is ideal to have it submitted in plenty of time for it to undergo the review process, which can take some time. If you submit a publication from research done during an away rotation between MS3-MS4 it is highly unlikely to be "published" in time for your residency application. It will still go on your application under "research experiences" of course... but won't be officially published.
And I would have to agree with Neuronix that having published Rad Onc research isn't "necessary" to match into this field. Some places actually will not offer you an interview if you have a very extensive basic science research background. Some programs are strictly clinical and don't offer much, if any... research opportunity during residency. So if you have a PhD they will often think "hey... this guy/gal wants to do research so lets offer the interview to someone who is a better fit." Its nice to have a research experience or two to show that you are interested in the field but I could actually imagine a scenario where you hurt your chances by doing research; i.e. you take too much time away from school for research... end up hurting your board scores and end up without any publications to show for it either. My own opinion is that an awful board score will hurt you more in getting interviews than not having "Rad Onc specific" research experience. The Oncology research experience you are describing should suffice for meeting the "research check-in-the-box," so to speak.
Of course... the best is to have BOTH and you are doing the right thing by starting early. As long as you have a realistic plan you can pull it off.