title: Virtual lymph node analysis to evaluate axillary lymph node coverage provided by tangential breast irradiation.
abstract: OBJECTIVE
  To investigate the coverage of axillary lymph node with tangential breast irradiation fields by using virtual lymph node (LN) analysis.
  
  
  METHODS
  Forty-eight women who were treated with whole breast irradiation after breast-conserving surgery were analyzed. The axillary and breast volumes were delineated according to the Radiation Therapy Oncology Group (RTOG) contouring atlas. To generate virtual LN contours, preoperative fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) scans with identifiable LN were fused with the CT scans, and the virtual LN contour were delineated on the CT.
  
  
  RESULTS
  The median level I and II axillary volume coverage percentages at the VD95% line were 33.5% (range, 5.3% to 90.4%) and 0.6% (range, 0.0% to 14.6%), respectively. Thirty-one LNs in 18 patients were delineated (26 in level I and 5 in level II). In the level I axilla, 84.6% of virtual LNs were encompassed by the 95% isodose line. In the level II axilla, by contrast, none of the virtual LNs were encompassed by the 95% isodose volumes. There was a substantial discrepancy between the RTOG contouring atlas-based axillary volume analysis and the virtual LN analysis, especially for the level I axillary coverage. The axillary volume coverage was associated with the body mass index (BMI) and breast volume.
  
  
  CONCLUSIONS
  The tangential breast irradiation did not deliver adequate therapeutic doses to the axillary region, particularly those in the level II axilla. Patients with small breast volumes or lower BMI showed reduced axillary coverage from the tangential breast fields. For axillary LN irradiation, individualized anatomy-based radiation fields for patients would be necessary.
authors: Department of Radiation Oncology, Kyungpook National University Hospital, Daegu, Korea.
authors: Shin-Hyung
authors: SH
authors: Park
authors: Department of Radiation Oncology, Kyungpook National University Hospital, Daegu, Korea.
authors: Jae-Chul
authors: JC
authors: Kim
authors: Department of Radiation Oncology, Kyungpook National University Hospital, Daegu, Korea.
authors: Jeong Eun
authors: JE
authors: Lee
authors: Department of Radiation Oncology, Kyungpook National University Hospital, Daegu, Korea.
authors: In-Kyu
authors: IK
authors: Park
keywords: Axilla; Breast neoplasm; Lymph nodes; Radiotherapy