title: Margin size is an independent predictor of local tumor progression after ablation of colon cancer liver metastases.
abstract: OBJECTIVE
  This study was designed to evaluate the relationship between the minimal margin size and local tumor progression (LTP) following CT-guided radiofrequency ablation (RFA) of colorectal cancer liver metastases (CLM).
  
  
  METHODS
  An institutional review board-approved, HIPPA-compliant review identified 73 patients with 94 previously untreated CLM that underwent RFA between March 2003 and May 2010, resulting in an ablation zone completely covering the tumor 4-8 weeks after RFA dynamic CT. Comparing the pre- with the post-RFA CT, the minimal margin size was categorized to 0, 1-5, 6-10, and 11-15 mm. Follow-up included CT every 2-4 months. Kaplan-Meier methodology and Cox regression analysis were used to evaluate the effect of the minimal margin size, tumor location, size, and proximity to a vessel on LTP.
  
  
  RESULTS
  Forty-five of 94 (47.9 %) CLM progressed locally. Median LTP-free survival (LPFS) was 16 months. Two-year LPFS rates for ablated CLM with minimal margin of 0, 1-5 mm, 6-10 mm, 11-15 mm were 26, 46, 74, and 80 % (p < 0.011). Minimal margin (p = 0.002) and tumor size (p = 0.028) were independent risk factors for LTP. The risk for LTP decreased by 46 % for each 5-mm increase in minimal margin size, whereas each additional 5-mm increase in tumor size increased the risk of LTP by 22 %.
  
  
  CONCLUSIONS
  An ablation zone with a minimal margin uniformly larger than 5 mm 4-8 weeks postablation CT is associated with the best local tumor control.
authors.affiliation: Section of Interventional Radiology, Department of Radiology, Memorial Sloan-Kettering Cancer Center, 1275 York Ave., Room H118, New York, NY 10065, USA.
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Wang
authors.forename: Constantinos T
authors.initials: CT
authors.lastname: Sofocleous
authors.forename: Joseph P
authors.initials: JP
authors.lastname: Erinjeri
authors.forename: Elena N
authors.initials: EN
authors.lastname: Petre
authors.forename: Mithat
authors.initials: M
authors.lastname: Gonen
authors.forename: Kinh G
authors.initials: KG
authors.lastname: Do
authors.forename: Karen T
authors.initials: KT
authors.lastname: Brown
authors.forename: Anne M
authors.initials: AM
authors.lastname: Covey
authors.forename: Lynn A
authors.initials: LA
authors.lastname: Brody
authors.forename: William
authors.initials: W
authors.lastname: Alago
authors.forename: Raymond H
authors.initials: RH
authors.lastname: Thornton
authors.forename: Nancy E
authors.initials: NE
authors.lastname: Kemeny
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Solomon
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D017115:Catheter Ablation / Q000379:methods*; D015331:Cohort Studies; D003110:Colonic Neoplasms / Q000401:mortality / Q000473:pathology* / Q000601:surgery; D016208:Databases, Factual; D018450:Disease Progression; D018572:Disease-Free Survival; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D053208:Kaplan-Meier Estimate; D008099:Liver / Q000473:pathology*; D008113:Liver Neoplasms / Q000401:mortality / Q000473:pathology / Q000556:secondary* / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009361:Neoplasm Invasiveness / Q000473:pathology; D011237:Predictive Value of Tests; D016016:Proportional Hazards Models; D012189:Retrospective Studies; D018570:Risk Assessment; D012737:Sex Factors; D018709:Statistics, Nonparametric; D016019:Survival Analysis; D013997:Time Factors; D016896:Treatment Outcome