You might want to check the Oncology Nursing web site and the University of Pennsylvania site:
www.ons.org and
http://cancer.med.upenn.edu/. I made up two oncology case studies for a project once. It was a lot of work. A great source of case studies are the books by Shirley Otto. She wrote 'Oncology Nursing' and a study guide to go with it. The study guide has case studies and correct answers. The Oncolgy Certified Nurse (OCN) exam is based on case studies. Otto's books were a big help to me.
good luck studying.