The significant risk of developing lymphedema may outweigh the benefit of receiving an extra boost of radiation to lymph nodes possibly involved in early-stage breast cancer. That is the conclusion of a study presented today at the 48th Annual Meeting of the American Society for Therapeutic Radiology and Oncology in Philadelphia.
Lymphedema is an uncomfortable swelling of a limb caused by a build-up of lymphatic fluid. This occurs when the lymph vessels are damaged and/or nodes are removed. The disruption of lymphatic flow prevents the proper drainage, causing a back-up of fluid. About 15-20% of women with breast cancer who have lymph nodes removed during surgery will develop lymphedema.
"We know radiation can increase one's risk of developing lymphedema, so it's important to determine whether the radiation technique or dose contributes," explained Shelly B. Hayes, M.D., a resident in the radiation oncology department at Fox Chase Cancer Center and lead author of the new study.
Standard therapy for women with early-stage breast cancer calls for radiation following a lumpectomy. The radiation field includes the whole affected breast and some of the lymph nodes under the arm, called the axillary lymph nodes.
Doctors may also irradiate the lymph nodes found in the upper axilla and above the clavicle (collar bone), depending on the number of nodes removed and the number that test positive for cancerous cells). Sometimes, an additional dose or "boost" of radiation is added to the axillary region.
"The reason we irradiate the lymph node regions is to prevent recurrence of disease in those locations," Hayes said. "When an aggressive lymph-node dissection is performed, the utility of additional radiation is questionable. This is the subject of some debate."
Hayes' study consisted of 2,581 women with early-stage breast cancer treated at Fox Chase Cancer Center with lumpectomy, axillary-node dissection and radiation between 1970 and 2005. A total of 2,174 patients (84%) were treated with radiation to the breast alone, 221patients (8.6%) were treated to the breast and supraclavicular lymph nodes (those above the collar bone) while 184 patients (7.1%) received an additional boost of radiation to the axillary nodes. The median follow-up was 81 months.
"The most striking result we found involved women who had more than four positive lymph nodes," explained Hayes. "They were four times more likely to develop lymphedema when treated with a boost, despite similar risks of nodal recurrences.
"Given the increased risk of lymphedema and the lack of evidence supporting improvements in nodal recurrences from the boost, we should carefully consider these results before delivering a boost to our patients," Hayes concluded.