title: Impact of margin status on outcomes following accelerated partial breast irradiation using single-lumen balloon-based brachytherapy.
abstract: OBJECTIVE
  To examine the impact of margin status on clinical outcomes for patients enrolled in the American Society of Breast Surgeons (ASBrS) MammoSite(®) Registry Trial.
  
  
  METHODS
  One thousand four hundred forty-nine cases of early-stage breast cancer underwent breast-conserving therapy with a single-lumen balloon-based applicator used to deliver adjuvant accelerated partial breast irradiation (34Gy in 10, bid fractions). One thousand two hundred fifty-five cases (87%) had invasive breast cancer (median size=10mm) and 194 cases (13%) had ductal carcinoma in situ (DCIS; median size=8mm).
  
  
  RESULTS
  Patients were stratified by margin status into negative (n=1326), close (<2mm; n=110), and positive (n=13) margins. One hundred twenty-three cases (8.5%) had close or positive margins. Overall, no statistical difference in the 6-year rate of ipsilateral breast tumor recurrence (IBTR) was noted for close margins compared with that of margin-negative patients (8.7% vs. 4.1%, p=0.10) or for positive margins compared with that of margin-negative patients (14.3% vs. 4.1%, p=0.41). In patients with DCIS, there was a statistically significant increase in IBTR with close margins (17.6% vs. 4.2%, p=0.004) and when close and positive margins were pooled (15.7% vs. 4.2%, p=0.01 with a nonsignificant reduction in disease-free survival for DCIS patients with close margins (82.4% vs. 90.8%, p=0.12). The increase in IBTR for close and close/positive patients was secondary to statistically significant increases in elsewhere failures rather than true recurrences/marginal misses.
  
  
  CONCLUSIONS
  Nonsignificant increases in the rates of IBTR were noted with close and positive margins for invasive cancer with further data required to validate these findings.
authors.affiliation: Department of Radiation Oncology, Washington University School of Medicine, St. Louis, MO, USA.
authors.forename: Chirag
authors.initials: C
authors.lastname: Shah
authors.forename: J Ben
authors.initials: JB
authors.lastname: Wilkinson
authors.forename: Martin
authors.initials: M
authors.lastname: Keisch
authors.forename: Peter
authors.initials: P
authors.lastname: Beitsch
authors.forename: Douglas
authors.initials: D
authors.lastname: Arthur
authors.forename: Maureen
authors.initials: M
authors.lastname: Lyden
authors.forename: Frank A
authors.initials: FA
authors.lastname: Vicini
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001918:Brachytherapy / Q000295:instrumentation* / Q000706:statistics & numerical data*; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000532:radiotherapy*; D019583:Dose Fractionation, Radiation; D005260:Female; D006801:Humans; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000453:epidemiology* / Q000517:prevention & control; D059351:Organ Sparing Treatments / Q000706:statistics & numerical data*; D015995:Prevalence; D011879:Radiotherapy Dosage; D012042:Registries; D018570:Risk Assessment; D016896:Treatment Outcome; D014481:United States / Q000453:epidemiology