Evaluation of level I and II axillary nodes included in the standard breast tangential fields and calculation of the administered dose: Results of a prospective study

Purpose: To evaluate if Level I and II axillary nodes are included in the s tandard breast tangential fields, and to calculate the dose administered. Methods and Materials: In 35 patients treated with conservative surgery and axillary dissection, three clips were surgically positioned: one at the be ginning of Level I one between Level I and IL and another at the end of Lev el II. The breast was irradiated with two tangential fields. On simulation films, the volume between the clips was scored as "entirely included" or "n ot entirely included" in the treatment fields. Computed tomography (CT) sca ns were performed; CT data were imported into a treatment planning system, and three-dimensional plans were devised. Axillary Levels I and II were del ineated on CT slices on the basis of anatomic landmarks. Fields and isodose curves previously obtained were superimposed to calculate the dose adminis tered to the first two axillary node levels and to 90% of both volumes. Results: On X-rays, the volume between clips corresponding to Level I was c ompletely included in the medial field in 66.7% of cases and in the lateral field in 63.7% of cases, whereas the volume of Level II was entirely inclu ded in the medial field in 54.5% of cases and in the lateral field in 45.4% of cases. The median dose administered to Level I and II was 38.58 Gy +/- 11.01 (range 3.46-47.14) and 20.65 Gy +/- 14.07 (range 0.95-38.94), respect ively. The median dose to 90% of both volumes of Level I and II was 6.75 Gy +/- 14.01 (range 1.9-39) and 1.75 Gy +/- 9.72 (range 0.8-29), respectively . Conclusion: The standard tangential fields do not entirely include Levels I and II axillary nodes. (C) 2001 Elsevier Science Inc.