Yes, graviola has been used very successfully for treatment of most types of cancer in humans. You might also consider paw paw extract - they are similar plants, but paw paw is actually stronger in some of the phytochemicals that fight cancer.
See this site for expert advice on graviola and paw paw.
www.alternativecancer.us
this site will also give you quite a bit of information on paw paw and graviola:
http://www.cancertutor.com/Cancer/Graviola.html
Sincerely,
Tre