How easy is it for a DO to get a fellowship after an Internal Medicine residency?

I know IM lets you specialize and get a fellowship in a variety of specialties such as cardiology, pulmonology, oncology, rheumatology, ID, endocrinology, gastroenterology, hematology etc... How accessible are these for a DO? Do most IM DOs go on to specialize or do they just stick with practicing general IM? After completing an IM residency are MDs and DOs on relatively equal footing? I really think I'd like to pursue oncology but am not sure what sorts of odds I have of that actually... How easy is it for a DO to get a fellowship after an Internal Medicine residency?
Source: Student Doctor Network - Category: Universities & Medical Training Authors: Source Type: forums