EPQ will not ever be included in your offer, however I did it and I found it EXTREMELY useful since it was related to medicine (investigating the potential use of cannabis as an analgesic in HIV Positive patients). I think the controversial nature of the topic helped since I was extensively asked about it at all 4 of my interviews, which probably helped in getting my offers because I would have stood out because of it. However, the most important things are your A-Levels and as the above person said, if you think that by doing an EPQ you will hinder your A Level performance then stay away. But if you work hard, you can certainly get a lot of things done. I managed to get 4 A*'s as well as an A in the EPQ and got offers from 3 medical schools including Cambridge and I am not particularly intelligent, just worked very, very hard. So if you are willing to work, I would certainly recommend doing it- make sure it is related to medicine and try and make it something that will sound good and stand out! And make sure you know your topic inside out because you will probably get asked about it at interview. If you need any more help, feel free to PM me.
Good Luck!