Congrats on getting into med school! 🙂
Here are some thoughts to start you off with (sorry for the random order, just typing them down off the top of my head):
1. As you said, keep an open mind about which specialty you'll choose. Many if not most med students end up changing their minds at least once (if not multiple times) during med school. You may find yourself doing the same.
2. Whatever rotation you're on (as an MS3), try to learn as much as you can from it. Don't just think, meh, whatever, I don't plan on going into this specialty, so I don't really care. Instead, even if you're sure you don't want to go into a particular specialty, think of it more like, this is the last time I'll probably be able to truly experience this specialty, so I'll try to learn all I can from it. Plus, it'll likely make you a better rounded doctor, which is especially helpful for a specialty like heme/onc.
3. If you know you're going into a particular specialty or subspecialty like heme/onc, consider doing a rotation in something seemingly unrelated but that might help inform oncology (e.g. pathology, radiology). This will help you see things from your colleagues' perspective and improve your own future practice.
4. Although you're in the IM heme/onc forum, you might find out you're more interested in pediatric cancer patients. Keep that in mind as well. (Similarly, if you really find some cancers far more interesting than others, say you really love learning all about leukemias and helping leukemia patients, then you might prefer to become a pediatric heme/onc.)
5. Consider the patient population you'll be working with. For example, neurology may be very interesting as an academic subject. But you'll be working mainly with an elderly patient population. Same with oncology. Are you ok with this?
6. Consider the bread and butter cases too. Although there are many differnt types of cancers, and many very interesting, in private practice you probably won't get to see all the rare zebras, or maybe if you do you'll end up referring them to local academic centers, but instead you'll most likely see the most common cancers (e.g. breast, prostate, colorectal, lung). Also some cancers you won't really get to dig your teeth into as much since other specialists will be running the show more (e.g. skin cancers with dermatologists especially BCCs and SCCs). Are you happy working the bread and butter cases?
7. Consider the underlying knowledge base for each specialty and if you find learning about it interesting. For example, heme/onc deals a lot with molecular and cell biology, immunology, pharmacology (among other subjects).
8. Consider the personality or culture of the field you're interested in. Are these the sorts of doctors you mesh well with?
9. You should get along well enough or professionally enough with your physician colleagues so they will be willing to refer patients to you, since as an oncologist, especially the first few years out, you'll depend on them for referrals and thus building your private practice (e.g. you'll most likely need to attend various tumor board meetings to network and so on). Otherwise you may not get much of a business.
10. In fact, generally speaking, don't neglect how the business side of things looks like. For example, consider the available practice environments for oncology (e.g. academia, hospital employed, VA, private practice), but also how many of them are being bought out. Consider how saturated some markets are. Consider the trend away from "buy and bill" and towards "white bagging" and how this effects oncologists and their practices.
11. Like many if not most fields, heme/onc is one of the less mobile fields, in my view. It's usually ideal to stay in a particular town for a long time, to take root in a particular place, so people know you, your name gets around, other doctors refer to you, etc. It's not like anesthesiology or emergency medicine where you can just pick up and move to a different town clear across the country one day if you don't want to live there anymore. You won't be as immediately mobile as an oncologist. Or, short of this, and since the reality is most people tend to stay in a particular place anyway so moving across the nation isn't really as big a concern, it may not be as easy to schedule vacations as an oncologist (especially your first years out) in contrast to specialties like anesthesiology or emergency medicine or radiology. But of course a major trade-off is anesthesiologists and emergency physicians and radiologists (except interventional or mammo) don't have their own patients and so hospitals and others aren't as loyal to them. Having no patients means you don't directly bring in money for the hospital. Oncology won't have this problem.
12. Some people like long-term care of patients, follow-up, etc. Others hate it and prefer quick interactions. You have to know yourself here.
13. Clinic. Your training in IM and heme/onc will likely be in academic institutions. But realize private practice is a very different practice environment. For instance, you won't have to see as many inpatients in PP as you do in academic centers; rather most will be outpatient. But this means tons of clinic. Do you like clinic? On the other hand, some physicians like ICU physicians really love working the unit, or can't stand clinic since it's boring to them or whatever, so they might not like PP heme/onc. Again, it's a personal choice.
14. Given oncology patients, you have to be the sort of person who is ok with delivering bad news. You don't have to be "good" at it (not yet - you'll learn that later). But the sort of person that is at least ok with it. Ideally, this includes being the sort of person who is sensitive to other people, their feelings and pains, not just in words, but also in body language, gestures, even in what's left "unspoken," to be able to communicate compassionately with patients and their loved ones about difficult topics (including death), etc. You can't have a tin ear for example, or if you do, you should hopefully be willing to try and overcome this, at least to some extent, so you can be a better listener.
15. Research is huge in getting into heme/onc, so try to do some research if you can. Of course, first author publications in prestigious journals are the best, this is pretty hard to do. But anything is good - case reports, posters, abstracts at conferences, of course journal publications, etc. Anything is good at this point.
16. SDN has a wealth of helpful advisors. For oncology, check out stuff by people like gutonc and rustbeltonc, among many others.
17. In my opinion, you don't really need to buy anything for med school apart from a stethoscope and maybe a couple of books. So don't buy tons of books right away. Wait and see what works best for you, what your med school uses, etc.
