Two large clinical trials which involved thousands of patients, and studied the benefit of radiation therapy to lymph nodes under the arm and/ or under the collarbone and breastbone, showed a reduction in the rate of recurrent breast cancer in lymph nodes in patients who received radiation therapy to their lymph nodes when compared with patients who did not receive radiation therapy to their lymph nodes. There was no difference in how long patients lived (i.e. survival benefit) between the two groups of patients.
Since we know that radiation to the breast after a lumpectomy is beneficial, is it also beneficial to include the lymph nodes in the radiation field especially for those who have tumor-involved nodes or larger tumors? Two trials that were published recently in the New England Journal of Medicine answer this question.
These trials were both very large–one included more than 1,800 patients from the U.S., Canada, and Australia (the MA 20 trial) and the second, the EORTC 22922-10925 trial, included 4,000 patients from Europe. Each trial had long follow-up of approximately 10 years and utilized current radiation techniques followed by thorough quality assurance programs. Both trials did not show an overall survival benefit to radiating the nodes in addition to the breast but there were fewer recurrences in the axilla in both studies. The EORTC trial did show that radiation to the nodes near the clavicle and sternum improved mortality from breast cancer but not overall survival. Fortunately the rate of recurrence in the lymph nodes was low in both trials, less than 3% for both those who received radiation to the nodes and those that did not. Likewise, axillary recurrences were low as well in both studies, less than 2% for both trials. In addition, overall survival rates in both trials were 80% or greater at 10 years despite the fact that the patients in these trials had either multiple tumor-positive nodes or negative nodes with more aggressive tumor features, such as a large tumor size. Since these trials were started 15 to 20 years ago and systemic treatments have improved since then, it is highly likely that survival rates are even better now.
Each trial also carefully investigated the side effects of radiation. Both trials showed an increase in the rate of lymphedema with radiation to the lymph nodes, 8% to 12% for those who received radiation to the nodes vs 4% to 10% for those who did not receive radiation to the nodes. Additionally, the MA 20 study showed increased rates of pneumonitis and skin changes, and the EORTC study showed an increased risk of pulmonary fibrosis. Both trials did not show a difference in cardiac problems between the 2 groups, but both studies concluded it was too early to assess cardiac issues.
Although both trials showed no overall survival benefit to radiating the nodes, some subgroups of patients may still benefit from radiation to the nodes. Both of these trials examined large groups of women who have very diverse tumor characteristics. Newer more current assays have enabled us categorize these diverse tumors into different prognostic groups based on their molecular makeup. These studies will help physicians individualize treatment for patients so it is more effective in the long run.