Stage I, II, IIIA, and Operable IIIC Breast Cancer
Radiation injury to the brachial plexus following adjuvant nodal radiation therapy is a rare clinical entity for breast cancer patients. In a single-institution study using current radiation techniques, 449 breast cancer patients treated with postoperative radiation therapy to the breast and regional lymphatics were followed for 5.5 years to assess the rate of brachial plexus injury. The diagnosis of such injury was made clinically with computerized tomography to distinguish radiation injury from tumor recurrence. When 54 Gy in 30 fractions was delivered to the regional nodes, the incidence of symptomatic brachial plexus injury was 1.0% compared with 5.9% when increased fraction sizes (45 Gy in 15 fractions) were used.
The rate of second malignancies following adjuvant radiation therapy is very low. Sarcomas in the treated field are rare, with the long-term risk at 0.2% at 10 years. One report suggests an increase in contralateral breast cancer for women younger than 45 years who have received chest wall radiation therapy after mastectomy. No increased risk of contralateral breast cancer occurs for women 45 years and older who receive radiation therapy. Techniques to minimize the radiation dose to the contralateral breast should be used to keep the absolute risk as low as possible. In nonsmokers, the risk of lung cancer as a result of radiation exposure during treatment is minimal when current dosimetry techniques are used. Smokers, however, may have a small increased risk of lung cancer in the ipsilateral lung.
Adjuvant Systemic Therapy
Stage and molecular features determine the need for adjuvant systemic therapy and the choice of modalities used. For example, estrogen and/or progesterone receptor–positive patients will receive hormone therapy. HER2 overexpression is an indication for using adjuvant trastuzumab, usually in combination with chemotherapy. When neither HER2 overexpression (e.g., triple negative, which is common in the basal-like tumors) nor hormone receptors are present, adjuvant therapy relies on chemotherapeutic regimens, which are often combined with experimental targeted approaches.
If ER status is used to select adjuvant treatment, the study should be performed in a well-established, skilled laboratory. Immunohistochemical assays appear to be at least as reliable as standard ligand-binding assays in predicting response to adjuvant endocrine therapy.