How can early-stage breast cancer be treated?

Complex. Always surgery: mastectomy and lumpectomy. In either case, a sentinel node biopsy in the armpit (axilla) will be done and possibly a full axillary node dissection. Usually (if > 1cm and/or estrogen receptor negative) chemotherapy and/or hormonal blockade. Often radiotherapy: if no mastectomy or if mastectomy and + lymph nodes.
Very Successfully. Primary rx is surgical, either lumpectomy or mastectomy (equal survival), with sentinel lymph node biopsy. If lump-x, rx must then include radiation therapy. Depending upon the stage and tumor-specific factors, chemotherapy may be recommended. Following these guidelines, most women diagnosed with early stage breast cancer will be cured.