First filter stations for lymphatic drainage of the breast are the axillary and internal mammary lymph nodes.
Incidence of. metastatic involvement of the internal mammary nodes is between 4-9% in patients with axillary node negative breast cancer and between 16-65% in patients with axillary node positive breast cancer.
Whole breast irradiation plus regional nodal irradiation significantly improved disease free survival, but not overall survival, in a randomized, multicenter phase 3 trial of women with node positive or high risk, node negative disease treated with survival improved from 84% for whole breast irradiation to 89.7% for whole breast radiation plus RNI, but overall survival was not statistically significant.
The addition of regional nodal irradiation (RNI)to WBI results in a 42% reduction in local regional recurrence in a 36% reduction in distant recurrence in patients treated with the BCT, and disease-free survival at five years after radiation therapy increased 33% if RNI was also done (Whelan T et al).
Risks for RNI include pain, lymphedema, pneumonitis, brachial plexus damage, limitation of range of motion of the shoulder, malignancy, radiation dermatitis, and poor cosmetic outcome.
In a random study 1832 women with node positive or high risk negative breast cancer assigned to nodal radiation or control group (treated with whole irradiation)10 year follow up showed no significant group difference in survival, with the rate of 82.2% in the nodal radiated group and 81.8% in the control group (Whelan TJ et al), but reduced the rate of breast cancer recurrence.
In a randomly assigned trial of women (4004) who had a central or medial breast cancer, irrespective of axillary involvement, or an externally located tumor with axillary involvement to undergo either whole breast or thoracic wall irradiation alone: in early breast cancer irradiation of the regional nodes had a marginal effect on overall survival, disease free survival and distant disease survival were improved and breast cancer mortality reduced (EORTC Radiation Oncology and Breast Cancer Groups).
Above data does not apply with axillary node negative cancers.
Recent trials show that, at a median follow-up of 10 years, irradiation of the regional lymph nodes is associated with an increased disease free survival attributed to a decrease in the risk of the development of distant metastases.
Contemporary radiation therapy facilitates the delivery of homogeneous dosage to nodal areas, while limiting the dose to normal tissues.
Present recommendations is that all breast cancer patients with positive nodes should be considered for locoregional irradiation.
Two large phase 3 randomized clinical trials demonstrated the disease free survival is associated with regional nodal irradiation when added to whole breast or chest radiation after surgery in node positive breast cancer or higher risk node negative breast cancer.
Regional nodal radiation result in substantial reduction in breast cancer mortality and recurrence.
Discrepancies exist over the clinical benefit of the use of internal mammary node radiation in patients with breast cancer:it might be beneficial for patients with medially or centrally located tumors.