Role of internal mammary node radiation as a part of modern breast cancer radiation therapy: A systematic review

Purpose 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. Methods and Materials 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). Results 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. Conclusions 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.