Role of Internal Mammary Node Radiation as a Part of Modern Breast Cancer Radiation Therapy: A Systematic Review

Despite data from multiple randomized trials, the role of internal mammary lymph node irradiation as a part of regional nodal irradiation (IMLN RT-RNI) remains unanswered. Recent noteworthy data and modern RT techniques might identify a subset of patients who will benefit from IMLN RT-RNI, lending insight into the balance between improved outcomes and acceptable toxicity. We evaluated the current role of IMLN RT-RNI by analyzing randomized, prospective, and retrospective data.

In accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, a review of the published data was performed using PubMed to evaluate published studies from 1994 to 2015. The information evaluated included the number of patients, follow-up period, technical aspects of RT, and outcomes (clinical outcomes, complications/toxicity).

We included 16 studies (4 randomized, 4 nonrandomized, 7 retrospective, and 1 meta-analysis). Although older randomized trials failed to show differences in clinical outcomes or toxicity with IMLN RT-RNI, recent randomized data suggest the potential for improved outcomes, including overall survival, with IMLN RT-RNI. Furthermore, nonrandomized data have suggested a potential benefit for central tumors with IMLN RT-RNI. Although recent data have suggested a potential increase in pulmonary complications with IMLN RT-RNI with the use of advanced radiation techniques, toxicity rates remain low with limited cardiac toxicity data available.

Increasing data from recent randomized trials support the use of IMLN RT-RNI. IMLN RT can be considered based on the inclusion of IMLN RT as a part of RNI in recent trials and the inclusion criteria from IMLN RT-RNI trials and for patients with central or medial tumors and axillary disease.