title: VMAT techniques for lymph node-positive left sided breast cancer.
abstract: OBJECTIVE
  To investigate the plan quality of two different volumetric modulated arc therapy (VMAT) techniques for lymph node-positive left-sided breast cancer.
  
  
  METHODS
  Two VMAT plans were generated for 10 lymph node-positive left-sided breast cancer patients: one plan using one single segment of a full rotation, typically an arc segment of 230° (1s-VMAT); and a second plan consisting of 2 small tangential arc segments of about 50° (2s-VMAT). For plan comparison, various dose and dose volume metrics (Dmean, D98%, D2% for target volumes, D2%, Dmean and Vx% for organs at risk (OAR)) were evaluated.
  
  
  RESULTS
  Both techniques fulfilled both clinical target dose and OAR goals. 1s-VMAT achieved a slightly better homogeneity and better target coverage (D2%= 54.2 ± 0.7 Gy, D98%= 30.3 ± 1.8 Gy) compared to 2s-VMAT (D2%= 55.0 ± 1.1 Gy, D98%= 29.9 ± 1.7 Gy). For geometrical reasons, OAR sparing was noticeable but not significant better using 2s-VMAT, particularly heart and contralateral breast. The heart received a mean dose of 4.4 ± 0.8 Gy using 1s-VMAT and 3.3 ± 1.0 Gy using 2s-VMAT; the contralateral breast received 1.5 ± 0.3 Gy and 0.9 ± 0.3 Gy, respectively.
  
  
  CONCLUSIONS
  A VMAT technique based on two small tangential arc segments enables improved OAR sparing; the differences between the two techniques in target coverage and homogeneity are minor. Patient age and -anatomy must be considered for each individual case when deciding which technique to be used.
authors.affiliation: Lake Constance Radiation Oncology Center Singen, Friedrichshafen, Germany. Electronic address: pasler@strahlentherapie-fn.de.
authors.forename: Marlies
authors.initials: M
authors.lastname: Pasler
authors.affiliation: Lake Constance Radiation Oncology Center Singen, Friedrichshafen, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Lutterbach
authors.affiliation: Lake Constance Radiation Oncology Center Singen, Friedrichshafen, Germany.
authors.forename: Mari
authors.initials: M
authors.lastname: Björnsgard
authors.affiliation: Lake Constance Radiation Oncology Center Singen, Friedrichshafen, Germany.
authors.forename: Ursula
authors.initials: U
authors.lastname: Reichmann
authors.affiliation: Lake Constance Radiation Oncology Center Singen, Friedrichshafen, Germany.
authors.forename: Susanne
authors.initials: S
authors.lastname: Bartelt
authors.affiliation: Department of Radiooncology, Medical University Vienna/AKH Wien, Vienna, Austria; Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University Vienna, Vienna, Austria.
authors.forename: Dietmar
authors.initials: D
authors.lastname: Georg
mesh_terms: D002277:Carcinoma / Q000532:radiotherapy* / Q000556:secondary*; D005260:Female; D006801:Humans; D008198:Lymph Nodes / Q000528:radiation effects; D008207:Lymphatic Metastasis; D058958:Organs at Risk / Q000528:radiation effects*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016896:Treatment Outcome; D000069584:Unilateral Breast Neoplasms / Q000532:radiotherapy*
keywords: OAR sparing; Risikoorganschonung; VMAT; left-sided breast cancer; linksseitiges Mammakarzinom