If you're exercising regularly and eating healthy, you're doing the right thing for surgury prep. If you use herbs, you might want to avoid those that either thin the blood or enhance circulation immediately before your operation. Examples are garlic, ginko biloba and gotu kola.
is an article about prostate cancer and nutrition. Here
is another. Eating right is no guarantee that you won't get cancer, but it can reduce the incidence and severity of the disease.
Best of luck to you. I'll say a prayer for you. Be sure to post after the surgury to let us know how you're doing.