title: Absolute risk reductions for local recurrence after postoperative radiotherapy after sector resection for ductal carcinoma in situ of the breast.
abstract: OBJECTIVE
  Evaluate the effects of radiotherapy after sector resection for ductal carcinoma in situ of the breast (DCIS) in patient groups as defined by age, size of the lesion, focality, completeness of excision and mode of detection.
  
  
  METHODS
  A total of 1,067 women in Sweden were randomly assigned to either postoperative radiotherapy (RT) or control from 1987 to 1999, and 1,046 were followed for a mean of 8 years. The main outcome was new ipsilateral breast cancer events and distant metastasis-free survival analyzed according to intention to treat.
  
  
  RESULTS
  There were 64 ipsilateral events in the RT arm and 141 in the control group corresponding to a risk reduction of 16.0 percentage points at 10 years (95% CI, 10.3% to 21.6%) and a relative risk of 0.40 (95% CI, 0.30 to 0.54). There was no statistically significant difference in distant metastasis-free survival. There was an effect modification by age, yielding a low effect of RT in women younger than 50, but substantial protection in women older than 60 years. The age effect was not confounded by focality, lesion size, completeness of excision, or detection mode. There was no group as defined by our stratification variables that had a low risk without radiotherapy.
  
  
  CONCLUSIONS
  Our results indicate that younger women have a low protective effect of conventional RT after sector resection. Older women benefit substantially. We caution that the age effect was seen in a subgroup analysis. Further search with conventional clinical variables for a low risk group that does not need RT does not seem fruitful.
authors.affiliation: Division of Cancer Studies, Thomas Guy House, 3rd Floor, King's College London, Guy's Campus, London SE1 9RT, United Kingdom. lars.holmberg@kcl.ac.uk
authors.forename: Lars
authors.initials: L
authors.lastname: Holmberg
authors.forename: Hans
authors.initials: H
authors.lastname: Garmo
authors.forename: Bengt
authors.initials: B
authors.lastname: Granstrand
authors.forename: Anita
authors.initials: A
authors.lastname: Ringberg
authors.forename: Lars-Gunnar
authors.initials: LG
authors.lastname: Arnesson
authors.forename: Kerstin
authors.initials: K
authors.lastname: Sandelin
authors.forename: Per
authors.initials: P
authors.lastname: Karlsson
authors.forename: Harald
authors.initials: H
authors.lastname: Anderson
authors.forename: Stefan
authors.initials: S
authors.lastname: Emdin
mesh_terms: D000368:Aged; D001943:Breast Neoplasms / Q000532:radiotherapy* / Q000601:surgery*; D018270:Carcinoma, Ductal, Breast / Q000532:radiotherapy / Q000601:surgery; D002285:Carcinoma, Intraductal, Noninfiltrating / Q000532:radiotherapy* / Q000601:surgery*; D005260:Female; D006801:Humans; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000209:etiology / Q000517:prevention & control*; D011184:Postoperative Period; D040242:Risk Reduction Behavior; D015996:Survival Rate; D013548:Sweden; D016896:Treatment Outcome