title: Association of Radiotherapy Boost for Ductal Carcinoma In Situ With Local Control After Whole-Breast Radiotherapy.
abstract: OBJECTIVE
  The use of a radiotherapy (RT) boost to the tumor bed after whole-breast RT (WBRT) for ductal carcinoma in situ (DCIS) is largely extrapolated from invasive cancer data, but robust evidence specific to DCIS is lacking.
  
  
  OBJECTIVE
  To compare ipsilateral breast tumor recurrence (IBTR) in women with DCIS treated with vs without the RT boost after breast-conserving surgery and WBRT.
  
  
  METHODS
  This retrospective analysis pooled deidentified patient-level data from 10 academic institutions in the United States, Canada, and France from January 1, 1980, through December 31, 2010. All patients had newly diagnosed pure DCIS (no microinvasion), underwent breast-conserving surgery, and received WBRT with or without the boost with a minimum of 5 years of follow-up required for inclusion in the analysis. Given the limited events after WBRT, an a priori power analysis was conducted to estimate the DCIS sample size needed to detect the anticipated benefit of the boost. Data were uniformly recoded at the host institution and underwent primary and secondary reviews before analysis. Sample size calculations (ratio of patients who received the boost dose to those who did not, 2:1; α = .05; power = 80%) estimated that 2982 cases were needed to detect a difference of at least 3%. The final analysis included 4131 patients (2661 in the boost group and 1470 in the no-boost group) with a median follow-up of 9 years and media boost dose of 14 Gy. Data were collected from July 2011 through February 2014 and analyzed from March 2014 through August 2015.
  
  
  METHODS
  Radiotherapy boost vs no boost.
  
  
  METHODS
  Ipsilateral breast tumor recurrence.
  
  
  RESULTS
  The analysis included 4131 patients (median [SD] age, 56.1 [10.9] years; range, 24-88 years). Patients with positive margins, unknown estrogen receptor status, and comedo necrosis were more likely to have received an RT boost. For the entire cohort, the boost was significantly associated with lower IBTR (hazard ratio [HR], 0.73; 95% CI, 0.57-0.94; P = .01) and with IBTR-free survival (boost vs no-boost groups) of 97.1% (95% CI, 0.96-0.98) vs 96.3% (95% CI, 0.95-0.97) at 5 years, 94.1% (95% CI, 0.93-0.95) vs 92.5% (95% CI, 0.91-0.94) at 10 years, and 91.6% (95% CI, 0.90-0.93) vs 88.0% (95% CI, 0.85-0.91) at 15 years. On multivariable analysis accounting for confounding factors, the boost remained significantly associated with reduced IBTR (HR compared with no boost, 0.68; 95% CI, 0.50-0.91; P = .01) independent of age and tamoxifen citrate use.
  
  
  CONCLUSIONS
  This patient-level analysis suggests that the RT boost confers a statistically significant benefit in decreasing IBTR across all DCIS age groups, similar to that seen in patients with invasive breast cancer. These findings suggest that a DCIS RT boost to the tumor bed could be considered to provide an added incremental benefit in decreasing IBTR after a shared discussion between the patient and her radiation oncologist.
authors.affiliation: Smilow Cancer Center, Department of Therapeutic Radiology, Yale School of Medicine, New Haven, Connecticut.
authors.forename: Meena S
authors.initials: MS
authors.lastname: Moran
authors.affiliation: Department of Biostatistics, Yale School of Public Health, New Haven, Connecticut.
authors.forename: Yinjun
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: Department of Biostatistics, Yale School of Public Health, New Haven, Connecticut.
authors.forename: Shuangge
authors.initials: S
authors.lastname: Ma
authors.affiliation: Department of Radiation Therapy, Institut Curie, Paris, France.
authors.forename: Youlia
authors.initials: Y
authors.lastname: Kirova
authors.affiliation: Department of Radiation Therapy, Institut Curie, Paris, France.
authors.forename: Alain
authors.initials: A
authors.lastname: Fourquet
authors.affiliation: Department of Radiation Therapy, Oakland University William Beaumont School of Medicine, Royal Oak, Michigan.
authors.forename: Peter
authors.initials: P
authors.lastname: Chen
authors.affiliation: Department of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston.
authors.forename: Karen
authors.initials: K
authors.lastname: Hoffman
authors.affiliation: Department of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston.
authors.forename: Kelly
authors.initials: K
authors.lastname: Hunt
authors.affiliation: Department of Radiation Oncology, Harvard Medical School, Dana Farber Cancer Institute, Boston, Massachusetts.
authors.forename: Julia
authors.initials: J
authors.lastname: Wong
authors.affiliation: Department of Radiation Oncology, Harvard Medical School, Dana Farber Cancer Institute, Boston, Massachusetts.
authors.forename: Lia M
authors.initials: LM
authors.lastname: Halasz
authors.affiliation: Department of Radiation Oncology, University of Pennsylvania, Philadelphia.
authors.forename: Gary
authors.initials: G
authors.lastname: Freedman
authors.affiliation: Department of Radiation Oncology, University of Pennsylvania, Philadelphia.
authors.forename: Robert
authors.initials: R
authors.lastname: Prosnitz
authors.affiliation: Department of Radiation Oncology, University of Montreal, Hôpital Maisonneuve-Rosemont, Montreal, Quebec, Canada.
authors.forename: Michael
authors.initials: M
authors.lastname: Yassa
authors.affiliation: Department of Radiation Oncology, University of Montreal, Hôpital Maisonneuve-Rosemont, Montreal, Quebec, Canada.
authors.forename: David H A
authors.initials: DHA
authors.lastname: Nguyen
authors.affiliation: Department of Radiation Oncology, McGill University Health Centre, Montreal, Quebec, Canada.
authors.forename: Tarek
authors.initials: T
authors.lastname: Hijal
authors.affiliation: Department of Radiation Therapy, Robert Wood Johnson Medical School, New Brunswick, New Jersey.
authors.forename: Bruce G
authors.initials: BG
authors.lastname: Haffty
authors.affiliation: Department of Radiation Oncology, British Columbia Cancer Agency, Victoria, British Columbia, Canada.
authors.forename: Elaine S
authors.initials: ES
authors.lastname: Wai
authors.affiliation: Department of Radiation Oncology, British Columbia Cancer Agency, Victoria, British Columbia, Canada.
authors.forename: Pauline T
authors.initials: PT
authors.lastname: Truong
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000532:radiotherapy*; D002285:Carcinoma, Intraductal, Noninfiltrating / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000517:prevention & control*; D018714:Radiotherapy, Adjuvant; D055815:Young Adult