Col-lateral damage.

Top Line: While we know that the lateral extent of the radiation field border covering the axilla seems to be associated with lymphedema risk, it’s not so clear what in particular we’re trying to avoid.
The Study: This study took a detailed look at which parts of the axilla are associated with lymphedema risk in a cohort of over 250 women who received regional nodal radiation for breast cancer. The axilla was contoured into 8 separate anatomically-defined regions. The biggest difference in these regions and your standard axillary volumes was the inclusion of much more supero-lateral portions (in front of and lateral to the humeral head). They then associated lymphedema risk with a variety of dose levels to each region, and dose to the region of the axillary-lateral thoracic vessel junction (ALTJ) seemed most important. Anatomically, this region typically falls just lateral to level II where the lateral thoracic vessels branch from the axillary vessels. On 2D-imaging, it typically falls just under and/or lateral to the humeral head. As you can imagine, the decision to extend the lateral field border beyond the humeral head plays a big role in ALTJ dose. The best dosimetric cut-off for lymphedema risk was a minimum dose of 38.6 Gy to the ALTJ: With a minimum dose above and below this threshold, the risk of lymphedema was 37% versus 6%.
TBL: Minimizing dose specifically to the region of the axillary-lateral thoracic junction is associated with a lower risk of lymphedema in women receiving radiation for breast cancer. | Gross, Int J Radiat Oncol Biol Phys 2019


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