The oncologist makes decisions about which chemo and how much, how often based on the individual person's diagnosis.
If the pathology of the cancer shows that the cancer is hormone positive then additional treatments are usually recommended. Tamoxifen or aromatose inhibitors for those with ER and PR positive cancers. These are in tablet form. If the cancer is HER positive then that person is given Herceptin. This is not chemo but is a drug that helps to prevent the cancer from recurring. It is usually given by infusion (like chemo) every 3 weeks for about a year I think.
Hope this answers your question. Take care. Deanne xx