Role of radiation in early breast cancers
Early-stage breast cancer is defined by tumors that have not spread beyond the breast and are limited to the axillary lymph nodes. This includes ductal carcinoma in situ, stages IA and 1B, stages IIA and IIB, and stage IIIA breast cancers.
The most common type of breast cancer is ductal carcinoma, in which the cells of the milk ducts that arise in the breast glands (lobules) to the nipple become abnormal. This includes ductal carcinoma in situ in which the abnormal cells are found in the lining of the ducts, but they have not spread outside the duct and recognized as a very early stage of ductal carcinoma.
Breast cancer can also begin in the cells of the lobules and in other tissues in the breast. Invasive breast cancer is a term used when breast cancer has spread from where it began in the ducts or lobules to the surrounding tissue. Stages I, II and IIIA are determined by the size of the tumor and the presence or absence of lymph nodes with evidence of cancer. These breast cancers, when diagnosed are amenable to treatment with good outcomes.
In Stage 1 breast cancer is contained to only the area where the first abnormal cells began to develop and is classified in to IA and IB – in Ia, the tumor is smaller than 2 cm AND has not spread to the lymph nodes, while in Ib, adjacent lymph nodes have cancer evidence with very tiny clusters of cells of about 0.2mm to 2.0 mm. In stage IIA, the tumor is less than 2 cm and less than four axillary lymph nodes have cancer cells present, or the tumor size is between 2 and 5 cm and has not yet spread to the lymph nodes.
Stage IIB tumors are between the 2 and 5 cm, or greater but has spread to less than four axillary lymph nodes. Stage IIIA tumors can be 2-5 cm or greater, but spread to 4-9 axillary nodes. Oncologists consider radiotherapy, neoadjuvant chemotherapy, or endocrine therapy, based on individual patient factors. Adjuvant hormone therapy is provided if breast cancer patients express hormone receptors, and can be the only therapy provided to cure very early breast cancers. However, hormone therapy is not excluded if radiation therapy or surgery are chosen as part of the treatment regimen.
Radiation therapy is a fundamental part in the management of early-stage breast cancer. The trend these days is to try to conserve as much breast tissue (breast conserving therapy-lumpectomy) as possible, as opposed to the initial management of radical surgical dissections with or without radiotherapy.
Most patients with Stage 1 are treated with radiotherapy. The goal is to kill any remaining evidence of disease after lumpectomy. Radiation therapy begins 3-4 weeks post-surgery. Commonly, traditional or whole breast radiation therapy uses external beam radiation that is highly focused and targets the cancerous area for 2-3 minutes, and requires at least 5 days a week for 5-7 weeks.
Certain patients may require a slightly higher dose of radiation over a shorter course of treatment, usually 3-4 weeks (accelerated radiation). Whole breast irradiation reduces the risk of local recurrence by about 60-65%. Additional radiation to the area should also be given in patients who are at the highest risk of even minimal residual disease (primary tumor bed and immediately surrounding breast parenchyma) to avoid recurrence. In addition, adjuvant hormonal treatment – which also carries side effects – can be avoided if radiotherapy is given.
Newer methods of internally delivering radiation targeting only the cancerous tissues are also being used.