The Study: MA.20 needs no introduction, but here's one anyway. It randomized women with node(+) or high-risk node(-) breast cancer to adjuvant whole breast radiation with or without RNI. An important point of the trial was that RNI fields were designed to omit the lower (levels I and II) dissected axilla except in women with >3 involved nodes or fewer than 10 nodes dissected. Here we have a nice nomogram, including an external validation cohort, estimating the risk of lymphedema based on three factors: BMI, number of nodes dissected, and extent of axillary nodal irradiation (none, limited, extensive). The nomogram breaks overall lymphedema risk into low (<5%), intermediate (5-10%), and high (>10%). In the validation cohort, 15% of women were low risk, 45% intermediate risk, and 40% high risk. The first big takeaway is that the extent of axillary dissection appeared to be the main driver of risk, as women with full dissection and no RNI had higher rates of lymphedema than those with sentinel lymph node biopsy (SLNB) and full axillary radiation. But that’s not to say extent of axillary radiation isn’t a big risk modifier. Basically, women with low BMI, SLNB with fewer than 3 axillary nodes, and no regional nodal radiation have a very low risk of lymphedema. Women with high BMI, a full axillary lymph node dissection with 4 or more nodes positive, and radiation to the full axilla have a very high risk of lymphedema. And of course there’s a whole spectrum in between: thus the nomogram.
Bottom Line: A nifty MA.20-based nomogram using BMI, extent of axillary dissection, and extent of axillary radiation can be added to your armamentarium for estimating individualized risk of lymphedema. | Gross, Int J Radiat Oncol Biol Phys, 2019