title: Is biological subtype prognostic of locoregional recurrence risk in women with pT1-2N0 breast cancer treated with mastectomy?
abstract: OBJECTIVE
  To examine locoregional and distant recurrence (LRR and DR) in women with pT1-2N0 breast cancer according to approximated subtype and clinicopathologic characteristics.
  
  
  METHODS
  Two independent datasets were pooled and analyzed. The study participants were 1994 patients with pT1-2N0M0 breast cancer, treated with mastectomy without radiation therapy. The patients were classified into 1 of 5 subtypes: luminal A (ER+ or PR+/HER 2-/grade 1-2, n=1202); luminal B (ER+ or PR+/HER 2-/grade 3, n=294); luminal HER 2 (ER+ or PR+/HER 2+, n=221); HER 2 (ER-/PR-/HER 2+, n=105) and triple-negative breast cancer (TNBC) (ER-/PR-/HER 2-, n=172).
  
  
  RESULTS
  The median follow-up time was 4.3 years. The 5-year Kaplan-Meier (KM) LRR were 1.8% in luminal A, 3.1% in luminal B, 1.7% in luminal HER 2, 1.9% in HER 2, and 1.9% in TNBC cohorts (P=.81). The 5-year KM DR was highest among women with TNBC: 1.8% in luminal A, 5.0% in luminal B, 2.4% in luminal HER 2, 1.1% in HER 2, and 9.6% in TNBC cohorts (P<.001). Among 172 women with TNBC, the 5-year KM LRR were 1.3% with clear margins versus 12.5% with close or positive margins (P=.04). On multivariable analysis, factors that conferred higher LRR risk were tumors>2 cm, lobular histology, and close/positive surgical margins.
  
  
  CONCLUSIONS
  The 5-year risk of LRR in our pT1-2N0 cohort treated with mastectomy was generally low, with no significant differences observed between approximated subtypes. Among the subtypes, TNBC conferred the highest risk of DR and an elevated risk of LRR in the presence of positive or close margins. Our data suggest that although subtype alone cannot be used as the sole criterion to offer postmastectomy radiation therapy, it may reasonably be considered in conjunction with other clinicopathologic factors including tumor size, histology, and margin status. Larger cohorts and longer follow-up times are needed to define which women with node-negative disease have high postmastectomy LRR risks in contemporary practice.
authors.affiliation: Radiation Therapy Program, British Columbia Cancer Agency, Vancouver Island Centre, University of British Columbia, Victoria, BC, Canada; Breast Cancer Outcomes Unit, British Columbia Cancer Agency, Vancouver Island Centre, University of British Columbia, Victoria, BC, Canada. Electronic address: ptruong@bccancer.bc.ca.
authors.forename: Pauline T
authors.initials: PT
authors.lastname: Truong
authors.affiliation: Department of Radiation Oncology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Betro T
authors.initials: BT
authors.lastname: Sadek
authors.affiliation: Radiation Therapy Program, British Columbia Cancer Agency, Vancouver Island Centre, University of British Columbia, Victoria, BC, Canada.
authors.forename: Maria F
authors.initials: MF
authors.lastname: Lesperance
authors.affiliation: Breast Cancer Outcomes Unit, British Columbia Cancer Agency, Vancouver Island Centre, University of British Columbia, Victoria, BC, Canada.
authors.forename: Cheryl S
authors.initials: CS
authors.lastname: Alexander
authors.affiliation: Department of Radiation Oncology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Mina
authors.initials: M
authors.lastname: Shenouda
authors.affiliation: Department of Radiation Oncology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Rita Abi
authors.initials: RA
authors.lastname: Raad
authors.affiliation: Department of Radiation Oncology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Alphonse G
authors.initials: AG
authors.lastname: Taghian
mesh_terms: D000704:Analysis of Variance; D001365:Axilla; D001943:Breast Neoplasms / Q000737:chemistry / Q000145:classification / Q000401:mortality / Q000473:pathology* / Q000601:surgery*; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D008197:Lymph Node Excision; D008198:Lymph Nodes / Q000473:pathology; D008408:Mastectomy; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000401:mortality / Q000473:pathology; D009367:Neoplasm Staging; D011379:Prognosis; D018719:Erb-b2 Receptor Tyrosine Kinases; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D064726:Triple Negative Breast Neoplasms / Q000401:mortality / Q000473:pathology / Q000601:surgery; D047368:Tumor Burden
chemical_list: D018719:Erb-b2 Receptor Tyrosine Kinases; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone