title: Long-term outcomes of hypofractionation versus conventional radiation therapy after breast-conserving surgery for ductal carcinoma in situ of the breast.
abstract: OBJECTIVE
  Whole-breast radiation therapy (XRT) after breast-conserving surgery (BCS) for ductal carcinoma in situ (DCIS) may decrease the risk of local recurrence, but the optimal dose regimen remains unclear. Past studies administered 50 Gy in 25 fractions (conventional); however, treatment pattern studies report that hypofractionated (HF) regimens (42.4 Gy in 16 fractions) are frequently used. We report the impact of HF (vs conventional) on the risk of local recurrence after BCS for DCIS.
  
  
  METHODS
  All women with DCIS treated with BCS and XRT in Ontario, Canada from 1994 to 2003 were identified. Treatment and outcomes were assessed through administrative databases and validated by chart review. Survival analyses were performed. To account for systematic differences between women treated with alternate regimens, we used a propensity score adjustment approach.
  
  
  RESULTS
  We identified 1609 women, of whom 971 (60%) received conventional regimens and 638 (40%) received HF. A total of 489 patients (30%) received a boost dose, of whom 143 (15%) received conventional radiation therapy and 346 (54%) received HF. The median follow-up time was 9.2 years. The median age at diagnosis was 56 years (interquartile range [IQR], 49-65 years). On univariate analyses, the 10-year actuarial local recurrence-free survival was 86% for conventional radiation therapy and 89% for HF (P=.03). On multivariable analyses, age <45 years (hazard ratio [HR] = 2.4; 95% CI: 1.6-3.4; P<.0001), high (HR=2.9; 95% CI: 1.2-7.3; P=.02) or intermediate nuclear grade (HR=2.7; 95% CI: 1.1-6.6; P=.04), and positive resection margins (HR=1.4; 95% CI: 1.0-2.1; P=.05) were associated with an increased risk of local recurrence. HF was not significantly associated with an increased risk of local recurrence compared with conventional radiation therapy on multivariate analysis (HR=0.8; 95% CI: 0.5-1.2; P=.34).
  
  
  CONCLUSIONS
  The risk of local recurrence among individuals treated with HF regimens after BCS for DCIS was similar to that among individuals treated with conventional radiation therapy.
authors.affiliation: University of Toronto, Toronto, Ontario, Canada; Department of Radiation Oncology, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada; Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada.
authors.forename: Nafisha
authors.initials: N
authors.lastname: Lalani
authors.affiliation: University of Toronto, Toronto, Ontario, Canada; Department of Radiation Oncology, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada; Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada.
authors.forename: Lawrence
authors.initials: L
authors.lastname: Paszat
authors.affiliation: Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada.
authors.forename: Rinku
authors.initials: R
authors.lastname: Sutradhar
authors.affiliation: Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada.
authors.forename: Deva
authors.initials: D
authors.lastname: Thiruchelvam
authors.affiliation: University of Toronto, Toronto, Ontario, Canada; Department of Anatomic Pathology, Sunnybrook Health Sciences Centre and Department of Laboratory Medicine and Pathobiology, Toronto, Ontario, Canada.
authors.forename: Sharon
authors.initials: S
authors.lastname: Nofech-Mozes
authors.affiliation: University of Toronto, Toronto, Ontario, Canada; Department of Anatomic Pathology, Sunnybrook Health Sciences Centre and Department of Laboratory Medicine and Pathobiology, Toronto, Ontario, Canada.
authors.forename: Wedad
authors.initials: W
authors.lastname: Hanna
authors.affiliation: University of Toronto, Toronto, Ontario, Canada; Department of Anatomic Pathology, Sunnybrook Health Sciences Centre and Department of Laboratory Medicine and Pathobiology, Toronto, Ontario, Canada.
authors.forename: Elzbieta
authors.initials: E
authors.lastname: Slodkowska
authors.affiliation: University of Toronto, Toronto, Ontario, Canada; Laboratory Medicine Program, University Health Network and Department of Laboratory Medicine and Pathobiology, Campbell Family Institute for Breast Cancer Research, Toronto, Ontario, Canada.
authors.forename: Susan J
authors.initials: SJ
authors.lastname: Done
authors.affiliation: University of Toronto, Toronto, Ontario, Canada; Laboratory Medicine Program, University Health Network and Department of Laboratory Medicine and Pathobiology, Toronto, Ontario, Canada.
authors.forename: Naomi
authors.initials: N
authors.lastname: Miller
authors.affiliation: University of Toronto, Toronto, Ontario, Canada; Laboratory Medicine Program, University Health Network and Department of Laboratory Medicine and Pathobiology, Toronto, Ontario, Canada.
authors.forename: Bruce
authors.initials: B
authors.lastname: Youngson
authors.affiliation: Pathology and Laboratory Medicine, London Health Sciences Centre and Saint Joseph's Health Care, London, Ontario, Canada.
authors.forename: Alan
authors.initials: A
authors.lastname: Tuck
authors.affiliation: Department of Pathology and Molecular Medicine, Kingston General Hospital, Kingston, Ontario, Canada.
authors.forename: Sandip
authors.initials: S
authors.lastname: Sengupta
authors.affiliation: Department of Anatomical Pathology, Juravinski Hospital, Hamilton Health Sciences, Hamilton, Ontario, Canada.
authors.forename: Leela
authors.initials: L
authors.lastname: Elavathil
authors.affiliation: Department of Pathology and Laboratory Medicine, Mount Sinai Hospital and Department of Laboratory Medicine and Pathobiology, Toronto, Ontario, Canada.
authors.forename: Martin C
authors.initials: MC
authors.lastname: Chang
authors.affiliation: Department of Anatomical Pathology, Thunder Bay Regional Health Sciences Centre, Thunder Bay, Ontario, Canada.
authors.forename: Prashant A
authors.initials: PA
authors.lastname: Jani
authors.affiliation: Pathology and Laboratory Medicine, Sudbury Regional Hospital, Sudbury, Ontario, Canada.
authors.forename: Michel
authors.initials: M
authors.lastname: Bonin
authors.affiliation: University of Toronto, Toronto, Ontario, Canada; Department of Radiation Oncology, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada; Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada. Electronic address: eileen.rakovitch@sunnybrook.ca.
authors.forename: Eileen
authors.initials: E
authors.lastname: Rakovitch
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D001943:Breast Neoplasms / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D002285:Carcinoma, Intraductal, Noninfiltrating / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D018572:Disease-Free Survival; D019583:Dose Fractionation, Radiation; D005260:Female; D006801:Humans; D015412:Mastectomy, Segmental; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000401:mortality; D009864:Ontario; D057216:Propensity Score; D011879:Radiotherapy Dosage; D018714:Radiotherapy, Adjuvant / Q000379:methods / Q000706:statistics & numerical data; D019233:Retreatment / Q000706:statistics & numerical data; D012306:Risk