title: Contouring Guidelines for the Axillary Lymph Nodes for the Delivery of Radiation Therapy in Breast Cancer: Evaluation of the RTOG Breast Cancer Atlas.
abstract: OBJECTIVE
  The purpose of this study was to identify the axillary lymph nodes on pretreatment diagnostic computed tomography (CT) of the chest to determine their position relative to the anatomic axillary borders as defined by the Radiation Therapy Oncology Group (RTOG) breast cancer atlas for radiation therapy planning.
  
  
  METHODS
  Pretreatment diagnostic CT chest scans available for 30 breast cancer patients with clinically involved lymph nodes were fused with simulation CT. Contouring of axillary levels I, II, and III according to the RTOG guidelines was performed. Measurements were made from the area of distal tumor to the anatomic borders in 6 dimensions for each level.
  
  
  RESULTS
  Of the 30 patients, 100%, 93%, and 37% had clinical involvement of levels I, II, and III, respectively. The mean number of lymph nodes dissected was 13.6. The mean size of the largest lymph node was 2.4 cm. Extracapsular extension was seen in 23% of patients. In 97% of patients, an aspect of the involved lymph node lay outside of the anatomic border of a level. In 80% and 83% of patients, tumor extension was seen outside the cranial (1.78 ± 1.0 cm; range, 0.28-3.58 cm) and anterior (1.27 ± 0.92 cm; range, 0.24-3.58 cm) borders of level I, respectively. In 80% of patients, tumor extension was seen outside the caudal border of level II (1.36 ± 1.0 cm, range, 0.27-3.86 cm), and 0% to 33% of patients had tumor extension outside the remaining borders of all levels.
  
  
  CONCLUSIONS
  To cover 95% of lymph nodes at the cranial and anterior borders of level I, an additional clinical target volume margin of 3.78 cm and 3.11 cm, respectively, is necessary. The RTOG guidelines may be insufficient for coverage of axillary disease in patients with clinical nodal involvement who are undergoing neoadjuvant chemotherapy, incomplete axillary dissection, or treatment with intensity modulated radiation therapy. In patients with pretreatment diagnostic CT chest scans, fusion with simulation CT should be considered for tumor delineation.
authors.affiliation: Department of Radiation Oncology, Robert H. Lurie Comprehensive Cancer Center of Northwestern University, Chicago, Illinois.
authors.forename: Michelle S
authors.initials: MS
authors.lastname: Gentile
authors.affiliation: Department of Radiology, Robert H. Lurie Comprehensive Cancer Center of Northwestern University, Chicago, Illinois.
authors.forename: Asad A
authors.initials: AA
authors.lastname: Usman
authors.affiliation: Department of Radiology, Robert H. Lurie Comprehensive Cancer Center of Northwestern University, Chicago, Illinois.
authors.forename: Erin I
authors.initials: EI
authors.lastname: Neuschler
authors.affiliation: Department of Radiation Oncology, Robert H. Lurie Comprehensive Cancer Center of Northwestern University, Chicago, Illinois.
authors.forename: Vythialinga
authors.initials: V
authors.lastname: Sathiaseelan
authors.affiliation: Department of Radiation Oncology, Robert H. Lurie Comprehensive Cancer Center of Northwestern University, Chicago, Illinois.
authors.forename: John P
authors.initials: JP
authors.lastname: Hayes
authors.affiliation: Department of Radiation Oncology, Loyola University, Chicago, Illinois. Electronic address: WMSMALL@lumc.edu.
authors.forename: William
authors.initials: W
authors.lastname: Small
mesh_terms: D000328:Adult; D000368:Aged; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D001365:Axilla; D017024:Chemotherapy, Adjuvant; D005260:Female; D006801:Humans; D008197:Lymph Node Excision / Q000706:statistics & numerical data; D008198:Lymph Nodes / Q000000981:diagnostic imaging*; D015182:Lymphatic Irradiation / Q000379:methods; D015409:Mastectomy, Radical / Q000706:statistics & numerical data; D015412:Mastectomy, Segmental / Q000706:statistics & numerical data; D008488:Medical Illustration; D008875:Middle Aged; D017410:Practice Guidelines as Topic; D011880:Radiotherapy Planning, Computer-Assisted; D014057:Tomography, X-Ray Computed; D047368:Tumor Burden; D000069584:Unilateral Breast Neoplasms / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000473:pathology / Q000532:radiotherapy