title: Phase II trial of proton beam accelerated partial breast irradiation in breast cancer.
abstract: OBJECTIVE
  Here, we report the results of our phase II, prospective study of proton beam accelerated partial breast irradiation (PB-APBI) in patients with breast cancer after breast conserving surgery (BCS).
  
  
  METHODS
  Thirty patients diagnosed with breast cancer were treated with PB-APBI using a single-field proton beam or two fields after BCS. The treatment dose was 30 cobalt gray equivalent (CGE) in six CGE fractions delivered once daily over five consecutive working days.
  
  
  RESULTS
  All patients completed PB-APBI. The median follow-up time was 59 months (range: 43-70 months). Of the 30 patients, none had ipsilateral breast recurrence or regional or distant metastasis, and all were alive at the last follow-up. Physician-evaluated toxicities were mild to moderate, except in one patient who had severe wet desquamation at 2 months that was not observed beyond 6 months. Qualitative physician cosmetic assessments of good or excellent were noted in 83% and 80% of the patients at the end of PB-APBI and at 2 months, respectively, and decreased to 69% at 3 years. A good or excellent cosmetic outcome was noted in all patients treated with a two-field proton beam at any follow-up time point except for one. For all patients, the mean percentage breast retraction assessment (pBRA) value increased significantly during the follow-up period (p=0.02); however, it did not increase in patients treated with two-field PB-APBI (p=0.3).
  
  
  CONCLUSIONS
  PB-APBI consisting of 30 CGE in six CGE fractions once daily for five consecutive days can be delivered with excellent disease control and tolerable skin toxicity to properly selected patients with early-stage breast cancer. Multiple-field PB-APBI may achieve a high rate of good-to-excellent cosmetic outcomes. Additional clinical trials with larger patient groups are needed.
authors.affiliation: Proton Therapy Center, Research Institute and Hospital, National Cancer Center, Goyang, Republic of Korea; Department of Radiation Oncology, Seoul National University College of Medicine, Republic of Korea.
authors.forename: Ji Hyun
authors.initials: JH
authors.lastname: Chang
authors.forename: Nam Kwon
authors.initials: NK
authors.lastname: Lee
authors.forename: Ja Young
authors.initials: JY
authors.lastname: Kim
authors.forename: Yeon-Joo
authors.initials: YJ
authors.lastname: Kim
authors.forename: Sung Ho
authors.initials: SH
authors.lastname: Moon
authors.forename: Tae Hyun
authors.initials: TH
authors.lastname: Kim
authors.forename: Joo-Young
authors.initials: JY
authors.lastname: Kim
authors.forename: Dae Yong
authors.initials: DY
authors.lastname: Kim
authors.forename: Kwan Ho
authors.initials: KH
authors.lastname: Cho
authors.forename: Kyung Hwan
authors.initials: KH
authors.lastname: Shin
mesh_terms: D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D018572:Disease-Free Survival; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015412:Mastectomy, Segmental / Q000379:methods; D008875:Middle Aged; D009361:Neoplasm Invasiveness / Q000473:pathology; D009364:Neoplasm Recurrence, Local / Q000401:mortality / Q000473:pathology* / Q000628:therapy; D009367:Neoplasm Staging; D011446:Prospective Studies; D061766:Proton Therapy / Q000009:adverse effects / Q000379:methods*; D011879:Radiotherapy Dosage; D018714:Radiotherapy, Adjuvant; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects / Q000379:methods*; D056910:Republic of Korea; D018570:Risk Assessment; D018709:Statistics, Nonparametric; D015996:Survival Rate; D013997:Time Factors; D016896:Treatment Outcome
keywords: Accelerated partial breast irradiation (APBI); Breast cancer; Proton beam radiotherapy