title: Effectiveness of radiation therapy in older women with ductal carcinoma in situ.
abstract: BACKGROUND
  For women with ductal carcinoma in situ (DCIS), radiation therapy after conservative surgery lowers the risk of recurrence. However, emerging evidence suggests that radiation therapy confers only a marginal absolute benefit for older women with DCIS. In a cohort of older women with DCIS, we sought to determine whether radiation therapy was associated with a clinically significant benefit.
  
  
  METHODS
  Using the Surveillance, Epidemiology, and End Results (SEER)-Medicare database from January 1, 1992, through December 31, 1999, we identified 3409 women aged 66 years or older treated with conservative surgery for DCIS. A proportional hazards model tested whether radiation therapy was associated with a lower risk of a combined outcome, defined as a subsequent ipsilateral in situ or invasive breast cancer reported by SEER and/or a subsequent mastectomy reported by Medicare claims. The 5-year event risk was determined for patients without and with high-risk features, which were defined as at least one of the following: age 66-69 years, tumor larger than 2.5 cm, comedo histology, and/or high grade. All statistical tests were two-sided.
  
  
  RESULTS
  Radiation therapy was associated with a lower risk for each component of the combined outcome (hazard ratio = 0.32, 95% confidence interval [CI] = 0.24 to 0.44). For high-risk patients, the 5-year event risk was 13.6% without radiation therapy versus 3.8% with radiation therapy (difference = 9.8%, 95% CI = 6.5 to 13.2; P<.001). For low-risk patients, the 5-year event risk was 8.2% without radiation therapy versus 1.0% with radiation therapy (difference = 7.2%, 95% CI = 3.6 to 10.9; P<.001). Among healthy women aged 66-79 years, the number needed to treat with radiation therapy to prevent one event in 5 years was 11 for high-risk patients and 15-16 for low-risk patients.
  
  
  CONCLUSIONS
  For older women with DCIS, radiation therapy appears to confer a substantial benefit that remains meaningful even among low-risk patients.
authors.affiliation: Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT, USA. bensmith@alumni.rice.edu
authors.forename: Benjamin D
authors.initials: BD
authors.lastname: Smith
authors.forename: Bruce G
authors.initials: BG
authors.lastname: Haffty
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Buchholz
authors.forename: Grace L
authors.initials: GL
authors.lastname: Smith
authors.forename: Deron H
authors.initials: DH
authors.lastname: Galusha
authors.forename: Justin E
authors.initials: JE
authors.lastname: Bekelman
authors.forename: Cary P
authors.initials: CP
authors.lastname: Gross
mesh_terms: D000367:Age Factors; D000368:Aged; D001943:Breast Neoplasms / Q000453:epidemiology / Q000532:radiotherapy* / Q000601:surgery; D002285:Carcinoma, Intraductal, Noninfiltrating / Q000453:epidemiology / Q000532:radiotherapy* / Q000601:surgery; D015986:Confounding Factors, Epidemiologic; D005260:Female; D006801:Humans; D015412:Mastectomy, Segmental; D009364:Neoplasm Recurrence, Local / Q000517:prevention & control*; D016017:Odds Ratio; D016016:Proportional Hazards Models; D018714:Radiotherapy, Adjuvant; D012107:Research Design; D012189:Retrospective Studies; D018570:Risk Assessment; D018426:SEER Program; D016896:Treatment Outcome; D014481:United States / Q000453:epidemiology