I'm not sure how they're doing things now, but when I applied to NYCOM, I didn't have an LOR from a doctor. I had submitted LORs from my undergrad pred-med committee and profs, but none from a do. I'm not sure if they're requiring a do letter now, but having one could only boost your application! Other than that, I had everything else submitted prior to me receiving an interview invite. Hope that helps somewhat.
If you have any other questions, just let me know!