title: Subsets of women with close or positive margins after breast-conserving surgery with high local recurrence risk despite breast plus boost radiotherapy.
abstract: OBJECTIVE
  (1) To examine the effect of surgical margin status on local recurrence (LR) and survival following breast-conserving therapy; (2) To identify subsets with close or positive margins with high LR risk despite whole breast radiotherapy (RT) plus boost.
  
  
  METHODS
  Subjects were 2,264 women with pT1-3, any N, M0 invasive breast cancer, treated with breast-conserving surgery and whole breast ± boost RT. Five-year Kaplan-Meier (KM) LR, breast cancer-specific and overall survival (BCSS and OS) were compared between cohorts with negative (n = 1,980), close (n = 222), and positive (n = 62) margins. LR rates were analyzed according to clinicopathologic characteristics. Multivariable Cox regression modeling and matched analysis of close/positive margin cases and negative margin controls were performed.
  
  
  RESULTS
  Median follow-up was 5.2 years. Boost RT was used in 92% of patients with close or positive margins. Five-year KM LR rates in the negative, close and positive margin cohorts were 1.3%, 4.0%, and 5.2%, respectively (p = 0.001). BCSS and OS were similar in the three margin subgroups. In the close/positive margin cohort, LR rates were 10.2% with age <45 years, 11.8% with Grade III, 11.3% with lymphovascular invasion (LVI), and 26.3% with ≥4 positive nodes. Corresponding rates in the negative margin cohort were 2.3%, 2.4%, 1.0%, and 2.4%, respectively. On Cox regression analysis of the entire cohort, close or positive margin, Grade III histology, ≥4 positive nodes, and lack of systemic therapy were significantly associated with higher LR risk. When close/positive margin cases were matched to negative margin controls, the difference in 5-year LR remained significant (4.25% vs. 0.7%, p < 0.001).
  
  
  CONCLUSIONS
  On univariable analysis, subsets with close or positive margins, in combination with age <45 years, Grade III, LVI, and ≥4 positive nodes, have 5-year LR >10% despite whole breast plus boost RT. These patients should be considered for more definitive surgery.
authors.affiliation: British Columbia Cancer Agency, Department of Radiation Oncology, Victoria, British Columbia, Canada.
authors.forename: Krystine
authors.initials: K
authors.lastname: Lupe
authors.forename: Pauline T
authors.initials: PT
authors.lastname: Truong
authors.forename: Cheryl
authors.initials: C
authors.lastname: Alexander
authors.forename: Mary
authors.initials: M
authors.lastname: Lesperance
authors.forename: Caroline
authors.initials: C
authors.lastname: Speers
authors.forename: Scott
authors.initials: S
authors.lastname: Tyldesley
mesh_terms: D000328:Adult; D000367:Age Factors; D000704:Analysis of Variance; D001943:Breast Neoplasms / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery*; D001955:British Columbia; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008207:Lymphatic Metastasis; D015412:Mastectomy, Segmental; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000401:mortality; D009367:Neoplasm Staging; D018365:Neoplasm, Residual; D011880:Radiotherapy Planning, Computer-Assisted; D012044:Regression Analysis; D019233:Retreatment