[Dose coverage of axillary target volumes using different field arrangements following breast conserving surgery for invasive breast cancer].

The purpose of this study was to investigate the dose coverage of sentinel lymph node (SLN) site, level I, II and III axillary target volumes using different field arrangements (standard or high tangent fields: STgF, HTgF and STgF + axillary-supraclavicular field: ASF) in N0 invasive breast cancer patients treated with breast conserving surgery. In 30 patients the SLN site was marked with titanium clip. They were treated with 3D-conformal radiotherapy. Retrospectively, for the purpose of this study, the SLN site and axillary target volumes were contoured, and three plans were generated for each patient using the original CT data. The prescribed dose was 50 Gy (2 Gy/fraction). The mean dose with STgF or HTgF was 33.1 and 49.1 Gy (p=0.0001) in the SLN site, 25.7 and 45.1 Gy (p<0.0001) in level I, 7.2 and 28.9 Gy (p<0.0001) in level II and 3.5 and 12.7 Gy (p=0.0003) in level III. The mean dose with STgF+ASF in level II or III was 45 and 46 Gy. The dose coverage is inadequate to all axillary levels with STgM. The target volumes should be delineated to give accurate dose estimation.