Radiotherapy instead of axillary lymph node dissection: evaluation of axillary lymph node dose coverage with whole breast radiotherapy

BACKGROUND: The purpose of this study was to investigate the dose coverage of sentinel lymph nodes (SLN), level I, II and III axillary volumes from tangent fields for breast cancer patients with positive SLN without axillary dissection. MATERIALS AND METHODS: In 30 patients with cN0 invasive breast cancer treated with breast conserving surgery and SLN biopsy, the SLN area was intraoperatively marked with a titanium clip. Retrospectively, the SLN area and axillary target volumes were contoured, and three plans [standard tangent fields (STgF), high tangent fields (HTgF), and STgF + axillary-supraclavicular field] were generated for each patient. The prescribed dose was standardized to 50 Gy in 2 Gy fractions to the isocenter. RESULTS: The mean dose with STgF or HTgF was 33.1 and 49.1 Gy (p = 0.0001) in the SLN area, 25.7 and 45.1 Gy (p < 0.0001) in the volume of level I, 7.2 and 28.9 Gy (p < 0.0001) in the level II and 3.5 and 12.7 Gy (p = 0.0003) in the level III. Adequate therapeutic doses to the level II or III volumes were delivered only with STgF + axillary-supraclavicular field. The mean dose of ipsilateral lung was the highest with the three-field-technique, 9.9 Gy. SLN area, level I, II or III were completely included in the HTgF with 93.3%, 73.3%, 13.3% and 0%, respectively. CONCLUSIONS: SLN area should be marked by surgical clip and axillary target volumes should be contoured to obtain accurate dose estimations. The use of HTgF improve axillary coverage.