@Scrbblechick: It all depends on the kind of cancer, location, staging, etc. Some people have cases where chemotherapy is most effective, while others have a type of cancer that responds best to radiation. My mom just had surgery and chemo when she had breast cancer. Her oncologist didn't even discuss radiation. Maybe because her tumor was pretty small and had very clear borders. She also had the most common (and treatable) form of breast cancer –Ductal Carcinoma In Situ, so that may have played a role, also.
Chemo was certainly effective for her. She will celebrate 25 years cancer free this year!