Are the axillary lymph nodes treated by standard tangent breast fields?

Background And Objectives: With the increasing use of sentinel lymph node biopsy, a growing proportion of women with early-stage invasive breast cancer are undergoing breast conserving surgery without a formal axillary lymph node dissection. A frequent question raised is whether the level I-II axillary lymph nodes are treated with standard breast tangent fields. In an attempt to answer this question, surgical clips placed at the time of the level I-II axillary lymph node dissection were used as a surrogate for the location of the nodes and the simulator films for tangent fields of 45 patients were analyzed.

Methods: Study criteria were as follows: five or more clips placed in the axilla, and all clips and the humeral head visualized on the medial tangent film. Clips were scored as "in" or "out" of the tangent field, as defined by the delineator wires. All technical parameters were analyzed to determine whether any reproducible techniques would consistently include all of the clips and, hypothetically, the axillary nodes at levels I and II.

Results: All clips were included in the medial tangent breast radiation field in only 38% (17 of 45) of cases.

Conclusions: The standard, two-field tangent breast fields do not reliably encompass the all level I-II axillary lymph nodes as defined by this study, but some of the nodes were treated in all 45 cases.