This is Dr. David
there are medical oncologist who specialist in giving chemotherapy and hormone therapy for cancer patients
and also radiation oncologist who specialize in giving radiation therapy for cancer patients.
you should see both doctors
but usually for most breast cancer surgery is the first course of treatment if the breast cancer is small in the breast and doesn't need to be shunk down for lumpectomy surgery.
and for both types of oncologist, the information obtained from the surgery, such as size of the breast cancer, spread to lymph nodes in the arm pit are needed to make decisions upon if you need chemotherapy or not
if you have a lumpectomy breast surgery, you will need radiation therapy to your breast.
so you should see both types of oncologist. but most surgeons will send you to them after your surgery.
but many university hospitals are having multidisciplinary breast cancer clinics where you see all types of specialist before your surgery right after your biopsy results and all of the doctors talk together to make a plan for your treatment.
ask your surgeon to refer you to talk to these types of oncologist before your surgery if you would like to know more about chemotherapy and radiation therapy treatments.
let me know if you have questions.