Hello there, Without more information, it s difficult to say what exactly you mean by combined modality treatment. The first step in a biopsy proven breast cancer is identification of the type of tumor. If this woman has LCIS (lobular carcinoma in situ), usually the treatment is excision of the area and treatment with a hormonal agent such as tamoxifen. In DCIS (ductal carcinoma in situ) the treatment is excision, usually followed by radiation. If the tumor is ER or PR (estrogen or progesterone receptor) positive, then tamoxifen is used for 10 years. In more advanced breast cancers such as lobular or ductal carincoma, the usual treatment is excision if it is stage I or stage II (depends on the size) with sentinel node biopsy. This is usually followed by chemotherapy and radiation, and again, if ER or PR+, then tamoxifen can also be used. Also Her2 is looked at, and a medication called herceptin can also be used in treatment. Finally, in more advanced breast cancer, chemotherapy is given first (neoadjuvant chemotherapy), followed by excision -this can be a modified radical mastectomy, followed by radiation and sometimes more chemo, plus tamoxifen and herceptin if the markers show sensitive to treatment by these adjuncts. Other factors can also play into mastectomy decision such as BRCA1 or BRCA-2 genes, and patients who are positive for these are usually recommend to undergo bilateral mastectomy even without cancer diagnosis. So to answer your question, it really depends on the type of cancer. The above mentioned treatments are standard of care in the US. I hope this is helpful. Please contact me if you have any further questions.