You don’t need it, no. One bit of advice; if you plan on pursuing this AND your hem/Onc program has a good transplant program AND you’re dead set on a career in BMT AND you have a flexible 3rd year schedule, id recommend spending at least 3 months on transplant rounding inpatient, going to research meetings going to clinic. It’ll basically allow you to complete 1/3 to 1/2 of what a transplant fellowship would’ve been all in your 3rd year. This is true of leukemia myeloma etc. you can get a ton of clinical experience in your 3rd year especially if you’re at a program with a busy transplant (or leukemia or myeloma or x) program. It definitely could preclude you from having to waste an extra year training. Some fellows have to do this because their programs didn’t were not large transplant Centers, or they were unable to find a position or felt unready for practice. But a short answer to your question is you don’t NEED the extra year although many fellows do end up taking this for a variety of reasons