The questions are really what you would expect: they want to get a sense of why you want to do oncology, what kind of oncologist you want to be and why (academic - lab based vs clinical; or private practice), details of your research and what you have learned from it, some random questions about anything else on your CV. Be honest, know about everything on your application and don't oversell yourself and you will be fine!
Be punctual, dress well, be nice to everyone you meet. Seem interested in the program, think of questions to ask every interviewer. When they run out of things to ask you they will invariably ask what questions you have for them. Ask about their research, why they chose that institution, specifics about the program (but don't ask questions that are answered on the program website, don't ask about the call schedule or vacation). Send a nice thank you email after the interview referring to something specific that you discussed. None of this is rocket science and no one expects you to know anything about oncology.