Late risk of relapse and mortality among postmenopausal women with estrogen responsive early breast cancer after 5 years of tamoxifen.
BACKGROUND
Letrozole after 5 years of adjuvant tamoxifen results in a significant reduction in risk of recurrence from estrogen receptor (ER) positive breast cancer. An individualized estimate of the risk of relapse and death after 5 years of tamoxifen could improve decisions regarding extended hormonal therapy.


METHODS
The British Columbia Breast Cancer Outcomes database was used to identify women aged 45 years or older at the time of diagnosis with early-stage (I-IIIA) breast cancer who received tamoxifen and were disease free 5 years after diagnosis. Ten-year breast cancer event rates and mortality were calculated as well as annualized hazard rates of recurrence.


RESULTS
A total of 1086 women were identified with a median age of 64 years and follow-up of 10.5 years. The relative risk (RR) of death was 3.1 (P=0.003) and for recurrence was 1.7 (P=0.037) for N1 (one to three positive nodes) versus N0 (zero nodes positive) disease. N2 (four to nine nodes positive) had a RR of 5.8 (P<0.001) for death and 3.0 (P=0.002) for recurrence. Low tumor grade and high ER level subgroups had a more favorable prognosis. Annual breast cancer risk between years 6 and 10 was, respectively, 2.2%, 3.5% and 7.6% for N0, N1 and N2 disease and 2.6% and 4.5% for T1 and T2 breast cancer.


CONCLUSIONS
T and N stages predicted late relapse and death from breast cancer in a population-based cohort of postmenopausal women. Risk estimates reported herein may be used to optimize decision making regarding adjuvant therapy after 5 years of tamoxifen.
Kennecke
H F
HF
Division of Medical Oncology, British Columbia (BC) Cancer Agency; Department of Medicine, University of British Columbia, Vancouver, BC; Breast Cancer Outcomes Unit. Electronic address: hkenneck@bccancer.bc.ca.
Olivotto
I A
IA
Department of Medicine, University of British Columbia, Vancouver, BC; Breast Cancer Outcomes Unit; Population and Preventive Oncology Programs; Victoria.
Speers
C
C
Breast Cancer Outcomes Unit; Population and Preventive Oncology Programs.
Norris
B
B
Department of Medicine, University of British Columbia, Vancouver, BC; Breast Cancer Outcomes Unit; Fraser Valley, BC Cancer Agency, Canada.
Chia
S K
SK
Division of Medical Oncology, British Columbia (BC) Cancer Agency; Department of Medicine, University of British Columbia, Vancouver, BC; Breast Cancer Outcomes Unit.
Bryce
C
C
Division of Medical Oncology, British Columbia (BC) Cancer Agency; Department of Medicine, University of British Columbia, Vancouver, BC; Breast Cancer Outcomes Unit.
Gelmon
K A
KA
Division of Medical Oncology, British Columbia (BC) Cancer Agency; Department of Medicine, University of British Columbia, Vancouver, BC; Breast Cancer Outcomes Unit.
D000368:Aged; D000369:Aged, 80 and over; D018931:Antineoplastic Agents, Hormonal / Q000627:therapeutic use*; D047072:Aromatase Inhibitors / Q000627:therapeutic use; D001943:Breast Neoplasms / Q000188:drug therapy / Q000401:mortality*; D001955:British Columbia; D018270:Carcinoma, Ductal, Breast / Q000188:drug therapy / Q000401:mortality; D018275:Carcinoma, Lobular / Q000188:drug therapy / Q000401:mortality; D017024:Chemotherapy, Adjuvant; D005260:Female; D006801:Humans; D000077289:Letrozole; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D009364:Neoplasm Recurrence, Local / Q000401:mortality*; D009367:Neoplasm Staging; D009376:Neoplasms, Hormone-Dependent / Q000188:drug therapy / Q000401:mortality*; D009570:Nitriles / Q000627:therapeutic use; D017698:Postmenopause; D011379:Prognosis; D012307:Risk Factors; D015996:Survival Rate; D013629:Tamoxifen / Q000627:therapeutic use*; D014230:Triazoles / Q000627:therapeutic use
D018931:Antineoplastic Agents, Hormonal; D047072:Aromatase Inhibitors; D009570:Nitriles; D014230:Triazoles; D013629:Tamoxifen; D000077289:Letrozole