title: Initial Report of a Prospective Dosimetric and Clinical Feasibility Trial Demonstrates the Potential of Protons to Increase the Therapeutic Ratio in Breast Cancer Compared With Photons.
abstract: OBJECTIVE
  To compare dosimetric endpoints between proton therapy (PT) and conventional radiation and determine the feasibility of PT for regional nodal irradiation (RNI) in women with breast cancer.
  
  
  METHODS
  From 2012 to 2014, 18 women (stage IIA-IIIB) requiring RNI prospectively enrolled on a pilot study. Median age was 51.8 years (range, 42-73 years). The cohort included breast-conserving therapy (BCT) and mastectomy patients and right- and left-sided cancers. Treatment targets and organs at risk were delineated on computed tomography scans, and PT and conventional plans were developed. Toxicity was prospectively recorded using Common Terminology Criteria for Adverse Events version 4.0. A Wilcoxon signed-rank sum test compared the dose-volume parameters. The primary endpoint was a reduction in cardiac V5.
  
  
  RESULTS
  Median follow-up was 20 months (range, 2-31 months). For all patients, the PT plan better met the dosimetric goals and was used for treatment. Proton therapy alone was used for 10 patients (9 postmastectomy, 1 after BCT) and combined proton-photon in 8 (6 BCT, 2 postmastectomy with immediate expander reconstruction). Proton therapy improved coverage of level 2 axilla (P=.0005). Adequate coverage of internal mammary nodes was consistently achieved with PT (median D95, 50.3 Gy; range, 46.6-52.1 Gy) but not with conventional radiation therapy (median D95, 48.2 Gy; range, 40.8-55 Gy; P=.0005). Median cardiac V5 was 0.6% with PT and 16.3% with conventional radiation (P<.0001). Median ipsilateral lung V5 and V20 were improved with PT (median V5 35.3% vs 60.5% [P<.0001]; and median V20, 21.6% vs 35.5% [P<.0001]). Grade 3 dermatitis developed in 4 patients (22%), which was the only grade 3 toxicity. No grade 4+ toxicities developed.
  
  
  CONCLUSIONS
  Proton therapy for RNI after mastectomy or BCT significantly improves cardiac dose, especially for left-sided patients, and lung V5 and V20 in all patients without excessive acute toxicity. Proton therapy simultaneously improves target coverage for the internal mammary nodes and level 2 axilla, which may positively impact long-term survival in breast cancer patients.
authors.affiliation: Department of Radiation Oncology, University of Florida, College of Medicine, Jacksonville, Florida. Electronic address: jbradley@floridaproton.org.
authors.forename: Julie A
authors.initials: JA
authors.lastname: Bradley
authors.affiliation: Department of Radiation Oncology, University of Florida, College of Medicine, Jacksonville, Florida.
authors.forename: Roi
authors.initials: R
authors.lastname: Dagan
authors.affiliation: Department of Radiation Oncology, University of Florida, College of Medicine, Jacksonville, Florida.
authors.forename: Meng Wei
authors.initials: MW
authors.lastname: Ho
authors.affiliation: Department of Radiation Oncology, University of Florida, College of Medicine, Jacksonville, Florida.
authors.forename: Michael
authors.initials: M
authors.lastname: Rutenberg
authors.affiliation: Department of Radiation Oncology, University of Florida, College of Medicine, Jacksonville, Florida.
authors.forename: Christopher G
authors.initials: CG
authors.lastname: Morris
authors.affiliation: Department of Radiation Oncology, University of Florida, College of Medicine, Jacksonville, Florida.
authors.forename: Zuofeng
authors.initials: Z
authors.lastname: Li
authors.affiliation: Department of Radiation Oncology, University of Florida, College of Medicine, Jacksonville, Florida.
authors.forename: Nancy P
authors.initials: NP
authors.lastname: Mendenhall
mesh_terms: D000328:Adult; D000368:Aged; D001365:Axilla; D005240:Feasibility Studies; D005260:Female; D005500:Follow-Up Studies; D006321:Heart / Q000000981:diagnostic imaging / Q000528:radiation effects*; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging / Q000528:radiation effects*; D015182:Lymphatic Irradiation / Q000009:adverse effects / Q000379:methods*; D008408:Mastectomy; D008875:Middle Aged; D058958:Organs at Risk / Q000000981:diagnostic imaging / Q000528:radiation effects*; D017785:Photons / Q000009:adverse effects / Q000627:therapeutic use; D010865:Pilot Projects; D011182:Postoperative Care; D011446:Prospective Studies; D061766:Proton Therapy / Q000009:adverse effects / Q000379:methods*; D011522:Protons / Q000009:adverse effects; D000069079:Radiation Exposure / Q000517:prevention & control; D011855:Radiodermatitis / Q000473:pathology; D011859:Radiography; D011879:Radiotherapy Dosage; D013997:Time Factors; D000069584:Unilateral Breast Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*
chemical_list: D011522:Protons