title: Local recurrence in women with stage I breast cancer: declining rates over time in a large, population-based cohort.
abstract: OBJECTIVE
  To evaluate whether local recurrence (LR) risk has changed over time among women with stage I breast cancer treated with breast-conserving therapy.
  
  
  METHODS
  Subjects were 5974 women aged ≥50 years diagnosis with pT1N0 breast cancer from 1989 to 2006, treated with breast-conserving surgery and radiation therapy. Clinicopathologic characteristics, treatment, and LR outcomes were compared among 4 cohorts stratified by year of diagnosis: 1989 to 1993 (n=1077), 1994 to 1998 (n=1633), 1999 to 2002 (n=1622), and 2003 to 2006 (n=1642). Multivariable analysis was performed, with year of diagnosis as a continuous variable.
  
  
  RESULTS
  Median follow-up time was 8.6 years. Among patients diagnosed in 1989 to 1993, 1994 to 1998, 1999 to 2002, and 2003 to 2006, the proportions of grade 1 tumors increased (16% vs 29% vs 40% vs 39%, respectively, P<.001). Surgical margin clearance rates increased from 82% to 93% to 95% and 88%, respectively (P<.001). Over time, the proportions of unknown estrogen receptor (ER) status decreased (29% vs 10% vs 1.2% vs 0.5%, respectively, P<.001), whereas ER-positive tumors increased (56% vs 77% vs 86% vs 86%, respectively, P<.001). Hormone therapy use increased (23% vs 23% vs 62% vs 73%, respectively, P<.001), and chemotherapy use increased (2% vs 5% vs 10% vs 13%, respectively, P<.001). The 5-year cumulative incidence rates of LR over the 4 time periods were 2.8% vs 1.7% vs 0.9% vs 0.8%, respectively (Gray's test, P<.001). On competing risk multivariable analysis, year of diagnosis was significantly associated with decreased LR (hazard ratio, 0.92 per year, P=.0003). Relative to grade 1 histology, grades 2, 3, and unknown were associated with increased LR. Hormone therapy use was associated with reduced LR.
  
  
  CONCLUSIONS
  Significant changes in the multimodality management of stage I breast cancer have occurred over the past 2 decades. More favorable-risk tumors were diagnosed, and margin clearance and systemic therapy use increased. These changes contributed to the observed declining LR rates among patients treated with breast-conserving therapy.
authors: Radiation Therapy Program and Breast Cancer Outcomes Unit, British Columbia Cancer Agency, Vancouver Island Centre, University of British Columbia, Victoria, British Columbia, Canada. Electronic address: canavanjoycelin@gmail.com.
authors: Joycelin
authors: J
authors: Canavan
authors: Radiation Therapy Program and Breast Cancer Outcomes Unit, British Columbia Cancer Agency, Vancouver Island Centre, University of British Columbia, Victoria, British Columbia, Canada.
authors: Pauline T
authors: PT
authors: Truong
authors: Radiation Therapy Program and Breast Cancer Outcomes Unit, British Columbia Cancer Agency, Vancouver Island Centre, University of British Columbia, Victoria, British Columbia, Canada.
authors: Sally L
authors: SL
authors: Smith
authors: Department of Mathematics and Statistics, University of Victoria, British Columbia, Canada.
authors: Linghong
authors: L
authors: Lu
authors: Department of Mathematics and Statistics, University of Victoria, British Columbia, Canada.
authors: Mary
authors: M
authors: Lesperance
authors: Department of Radiation Oncology, Tom Baker Cancer Centre, University of Calgary.
authors: Ivo A
authors: IA
authors: Olivotto
mesh_terms: D000368:Aged; D000970:Antineoplastic Agents / Q000627:therapeutic use; D001943:Breast Neoplasms / Q000737:chemistry / Q000453:epidemiology* / Q000473:pathology / Q000628:therapy*; D015331:Cohort Studies; D003131:Combined Modality Therapy / Q000639:trends; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D015412:Mastectomy, Segmental; D008875:Middle Aged; D015999:Multivariate Analysis; D009364:Neoplasm Recurrence, Local / Q000453:epidemiology*; D009367:Neoplasm Staging; D011879:Radiotherapy Dosage; D011960:Receptors, Estrogen / Q000032:analysis; D013997:Time Factors
chemical_list: D000970:Antineoplastic Agents; D011960:Receptors, Estrogen