Techniques for Internal Mammary Node Radiation
The clinical decision to include the internal mammary (IM) nodal chain into radiation treatment fields for breast cancer is complex, and the literature surrounding this decision is controversial and even conflicting [1–5]. However, with three high profile
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Techniques for Internal Mammary Node Radiation Jean Wright, Sook Kien Ng, and Oren Cahlon
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The clinical decision to include the internal mammary (IM) nodal chain into radiation treatment fields for breast cancer is complex, and the literature surrounding this decision is controversial and even conflicting [1–5]. However, with three recent high profile publications supporting the use of IM radiation even in relatively low-risk women, there will likely be an increasing trend toward IM radiation in the coming years [6]. The primary reasons not to treat these nodes are that it can be technically challenging and may increase exposure to the heart, lung, and contralateral breast. Ultimately, the decision to treat the IM nodes for an individual patient balances the estimated clinical benefit based on the patient’s scenario with the potential additional toxicity that may be conferred by treating this nodal group. This chapter will focus on the various techniques that may be employed to treat the IM nodes, rather than the complex decision-making involved for an individual patient. Several early publications compared techniques for post-mastectomy radiation (PMRT) and evaluated the different approaches with respect to chest wall and IM
J. Wright (*) • S.K. Ng Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University, Baltimore, MD, USA e-mail: [email protected] O. Cahlon Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, NY, USA © Springer International Publishing Switzerland 2016 J.R. Bellon et al. (eds.), Radiation Therapy Techniques and Treatment Planning for Breast Cancer, Practical Guides in Radiation Oncology, DOI 10.1007/978-3-319-40392-2_3
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coverage as well as the heart and lung dose [7, 8]. The two general techniques that emerged from these comparisons as providing the best IM coverage with relative sparing of the heart and lung, broadly categorized, were electron or electron/photon fields matched to shallow photon tangents and partially wide photon tangents. Two other emerging techniques for IM radiation have recently garnered attention, both developed primarily to improve IM coverage: proton therapy and intensity modulated radiation/volumetric modulated arc therapy (IMRT/VMAT). Regardless of the specific technique used, the first step in all cases is to clearly identify the target. Institutions vary in their implementation of contouring the breast or chest wall for treatment planning, but in the current era, it is critical, at a minimum, to contour the nodal targets. The current RTOG atlas for breast cancer (readily accessible at www.rtog.org/CoreLab/ContouringAtlases/BreastCancerAtlas. aspx) details the internal mammary chain anatomy. Generally, one contours the internal mammary artery and vein, which are almost always visible on a simple noncontrast planning CT, and co
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