title: Does adjuvant radiation therapy benefit women with small mammography-detected breast cancers?
abstract: BACKGROUND
  Women with small nonpalpable breast tumours have an excellent prognosis. The benefit of radiotherapy in this group of low-risk women is unknown.
  
  
  METHODS
  A cohort of 1595 women with stages i-iii invasive breast cancer treated with breast-conserving surgery were followed for local recurrence. Using t-tests, baseline demographic data and tumour characteristics were compared for the women who had palpable (n= 1023) and mammography-detected (n= 572) breast cancers. The 15-year actuarial risk of local recurrence was estimated using a Kaplan-Meier method, stratified for adjuvant radiation therapy (yes or no), tumour palpability (palpable or not), and tumour size (≤1 cm or >1 cm). Hazard ratios (hrs) and 95% confidence intervals (95% cis) were calculated using a multivariate Cox regression model. Results were considered statistically significant if 2-tailedpvalues were less than 0.05.
  
  
  RESULTS
  Among women with a nonpalpable tumour, the 15-year actuarial rates of local recurrence were, respectively, 13.9% and 18.3% for those treated and not treated with adjuvant radiation therapy (hr: 0.65; 95%ci: 0.40 to 1.06;p= 0.08). Among women with small nonpalpable breast cancers (≤1.0 cm), the rates were 14.6% and 13.4% respectively (p= 0.67). The absolute reduction in 15-year local recurrence was 11.0% for women with palpable tumours.
  
  
  CONCLUSIONS
  Our results suggest that women with small (<1 cm) screen-detected nonpalpable breast cancers likely derive little benefit from adjuvant radiotherapy; however, an adequately powered randomized trial would be required to make definitive conclusions.
authors.affiliation: Department of Medicine, University of Toronto, Toronto.
authors.forename: K
authors.initials: K
authors.lastname: Jerzak
authors.affiliation: McMaster University, Hamilton.
authors.forename: N
authors.initials: N
authors.lastname: Dudalski
authors.affiliation: Department of Medicine, Sunnybrook Odette Cancer Centre, Toronto;; Dalla Lana School of Public Health, University of Toronto, Toronto; and.
authors.forename: K
authors.initials: K
authors.lastname: Pritchard
authors.affiliation: Women's College Research Institute, Women's College Hospital, Toronto, ON.
authors.forename: P
authors.initials: P
authors.lastname: Sun
authors.affiliation: Dalla Lana School of Public Health, University of Toronto, Toronto; and; Women's College Research Institute, Women's College Hospital, Toronto, ON.
authors.forename: S A
authors.initials: SA
authors.lastname: Narod
keywords: Breast cancer; palpable breast tumours; radiation therapy