title: The ratio of positive to excised nodes identifies high-risk subsets and reduces inter-institutional differences in locoregional recurrence risk estimates in breast cancer patients with 1-3 positive nodes: an analysis of prospective data from British Columbia and the M. D. Anderson Cancer Center.
abstract: OBJECTIVE
  To examine the power of the nodal ratio (NR) of positive/excised nodes in predicting postmastectomy locoregional recurrence (LRR) in patients with 1-3 positive nodes (N+) and in identifying cohorts at similar risk across independent data sets.
  
  
  METHODS
  Data from 82 patients with 1-3 N+ treated without postmastectomy radiotherapy (PMRT) in the British Columbia (BC) randomized trial were compared with data from 462 patients treated without PMRT in prospective chemotherapy trials at the M. D. Anderson Cancer Center (MDACC). Kaplan-Meier LRR curves were compared between centers using the absolute number of N+ and nodal ratios.
  
  
  RESULTS
  The median number of excised nodes was 10 in BC and 16 in MDACC (p < 0.001). Examining LRR by number of N+, the 10-year LRR rate for patients with 1-3 N+ was higher in BC compared with MDACC (21.5% vs. 12.6%; p = 0.02). However, when examining LRR using NR, no differences were found between institutions. In patients with NR < or = 0.20, the 10-year LRR rate was 17.7% BC vs. 10.9% MDACC (p = 0.27). In patients with NR > or = 0.20, the 10-year LRR rate was 28.7% BC vs. 22.7% MDACC (p = 0.32). On Cox regression analysis, NR was a stronger prognostic factor compared with number of N +.
  
  
  CONCLUSIONS
  In patients with 1-3 N+, evaluating nodal positivity using NR reduced inter-institutional differences in LRR estimates that may exist due to variations in numbers of nodes excised. Nodal ratio >0.20 was associated with LRR >20%, warranting PMRT consideration. Nodal ratio may be useful for extrapolating data from prospective trials to clinical practices in which axillary staging extent vary.
authors.affiliation: Department of Radiation Oncology, British Columbia Cancer Agency - Vancouver Island Centre, British Columbia Cancer Agency, University of British Columbia, Victoria, BC, Canada. ptruong@bccancer.bc.ca
authors.forename: Pauline T
authors.initials: PT
authors.lastname: Truong
authors.forename: Wendy A
authors.initials: WA
authors.lastname: Woodward
authors.forename: Howard D
authors.initials: HD
authors.lastname: Thames
authors.forename: Joseph
authors.initials: J
authors.lastname: Ragaz
authors.forename: Ivo A
authors.initials: IA
authors.lastname: Olivotto
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Buchholz
mesh_terms: D000328:Adult; D000368:Aged; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D001365:Axilla; D001943:Breast Neoplasms / Q000188:drug therapy / Q000473:pathology* / Q000532:radiotherapy / Q000601:surgery; D003520:Cyclophosphamide / Q000008:administration & dosage; D005260:Female; D005472:Fluorouracil / Q000008:administration & dosage; D006801:Humans; D008197:Lymph Node Excision; D008207:Lymphatic Metastasis; D015411:Mastectomy, Modified Radical; D008727:Methotrexate / Q000008:administration & dosage; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local; D011446:Prospective Studies; D012044:Regression Analysis
chemical_list: D003520:Cyclophosphamide; D005472:Fluorouracil; D008727:Methotrexate