title: Proton radiotherapy for chest wall and regional lymphatic radiation; dose comparisons and treatment delivery.
abstract: OBJECTIVE
  The delivery of post-mastectomy radiation therapy (PMRT) can be challenging for patients with left sided breast cancer that have undergone mastectomy. This study investigates the use of protons for PMRT in selected patients with unfavorable cardiac anatomy. We also report the first clinical application of protons for these patients.
  
  
  METHODS
  Eleven patients were planned with protons, partially wide tangent photon fields (PWTF), and photon/electron (P/E) fields. Plans were generated with the goal of achieving 95% coverage of target volumes while maximally sparing cardiac and pulmonary structures. In addition, we report on two patients with unfavorable cardiac anatomy and IMN involvement that were treated with a mix of proton and standard radiation.
  
  
  RESULTS
  PWTF, P/E, and proton plans were generated and compared. Reasonable target volume coverage was achieved with PWTF and P/E fields, but proton therapy achieved superior coverage with a more homogeneous plan. Substantial cardiac and pulmonary sparing was achieved with proton therapy as compared to PWTF and P/E. In the two clinical cases, the delivery of proton radiation with a 7.2 to 9 Gy photon and electron component was feasible and well tolerated. Akimbo positioning was necessary for gantry clearance for one patient; the other was treated on a breast board with standard positioning (arms above her head). LAO field arrangement was used for both patients. Erythema and fatigue were the only noted side effects.
  
  
  CONCLUSIONS
  Proton RT enables delivery of radiation to the chest wall and regional lymphatics, including the IMN, without compromise of coverage and with improved sparing of surrounding normal structures. This treatment is feasible, however, optimal patient set up may vary and field size is limited without multiple fields/matching.
authors.affiliation: Department of Radiation Oncology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, 02114, USA. smacdonald@partners.org
authors.forename: Shannon M
authors.initials: SM
authors.lastname: MacDonald
authors.forename: Rachel
authors.initials: R
authors.lastname: Jimenez
authors.forename: Peter
authors.initials: P
authors.lastname: Paetzold
authors.forename: Judith
authors.initials: J
authors.lastname: Adams
authors.forename: Jonathan
authors.initials: J
authors.lastname: Beatty
authors.forename: Thomas F
authors.initials: TF
authors.lastname: DeLaney
authors.forename: Hanne
authors.initials: H
authors.lastname: Kooy
authors.forename: Alphonse G
authors.initials: AG
authors.lastname: Taghian
authors.forename: Hsiao-Ming
authors.initials: HM
authors.lastname: Lu
mesh_terms: D001943:Breast Neoplasms / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D008207:Lymphatic Metastasis / Q000532:radiotherapy*; D061766:Proton Therapy / Q000379:methods*; D011874:Radiometry; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D035441:Thoracic Wall / Q000528:radiation effects*