title: pN0(i+) breast cancer: treatment patterns, locoregional recurrence, and survival outcomes.
abstract: OBJECTIVE
  To examine treatment patterns, recurrence, and survival outcomes in patients with pN0(i+) breast cancer.
  
  
  METHODS
  Subjects were 5999 women with AJCC (6th edition) pT1-3, pN0-N1a, M0 breast cancer diagnosed between 2003 and 2006. Of these, 4342 (72%) had pN0, 96 (2%) had pN0(i+), 349 (6%) had pNmic (micrometastases>0.2 mm to ≤2 mm), and 1212 (20%) had pN1a (1-3 positive macroscopic nodes) disease. Treatment characteristics and 5-year Kaplan-Meier local recurrence, regional recurrence (RR), locoregional recurrence (LRR), and overall survival were compared between nodal subgroups. Multivariable analysis was performed using Cox regression modeling. A 1:3 case-match analysis examined outcomes in pN0(i+) cases compared with pN0 controls matched for similar tumor and treatment characteristics.
  
  
  RESULTS
  Median follow-up was 4.8 years. Adjuvant systemic therapy use increased with nodal stage: 81%, 92%, 95%, and 94% in pN0, pN0(i+), pNmic, and pN1a disease, respectively (P<.001). Nodal radiation therapy (RT) use also increased with nodal stage: 1.7% in pN0, 27% in pN0(i+), 33% in pNmic, and 63% in pN1a cohorts (P<.001). Five-year Kaplan-Meier outcomes in pN0 versus pN0(i+) cases were as follows: local recurrence 1.7% versus 3.7% (P=.20), RR 0.5% versus 2.2% (P=.02), and LRR 2.1% versus 5.8% (P=.02). There were no RR events in 26 patients with pN0(i+) disease who received nodal RT and 2 RR events in 70 patients who did not receive nodal RT. On multivariable analysis, pN0(i+) was not associated with worse locoregional control or survival. On case-match analysis, LRR and overall survival were similar between pN0(i+) and matched pN0 counterparts.
  
  
  CONCLUSIONS
  Nodal involvement with isolated tumor cells is not a significant prognostic factor for LRR or survival in this study's multivariable and case-match analyses. These data do not support the routine use of nodal RT in the setting of pN0(i+) disease. Prospective studies are needed to define optimal locoregional management for women with pN0(i+) breast cancer.
authors.affiliation: Radiation Therapy Program, Vancouver Island and Vancouver Centre, British Columbia Cancer Agency, University of British Columbia, Victoria, BC, Canada; Breast Cancer Outcomes Unit, British Columbia Cancer Agency, Vancouver, BC, Canada.
authors.forename: Irene
authors.initials: I
authors.lastname: Karam
authors.forename: Maria F
authors.initials: MF
authors.lastname: Lesperance
authors.forename: Tanya
authors.initials: T
authors.lastname: Berrang
authors.forename: Caroline
authors.initials: C
authors.lastname: Speers
authors.forename: Scott
authors.initials: S
authors.lastname: Tyldesley
authors.forename: Pauline T
authors.initials: PT
authors.lastname: Truong
mesh_terms: D001365:Axilla; D001943:Breast Neoplasms / Q000188:drug therapy / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008207:Lymphatic Metastasis; D008408:Mastectomy / Q000379:methods; D008875:Middle Aged; D015999:Multivariate Analysis; D061206:Neoplasm Micrometastasis / Q000473:pathology / Q000628:therapy; D009364:Neoplasm Recurrence, Local / Q000401:mortality; D009367:Neoplasm Staging; D011379:Prognosis