Original StudyRisk of Recurrence or Contralateral Breast Cancer More than 5 Years After Diagnosis of Hormone Receptor-Positive Early-Stage Breast Cancer

BackgroundThree large studies have shown a survival benefit from 10 years of adjuvant hormone therapy (AHT). We evaluated the risk of an event 5 years after the initial breast cancer (BC) diagnosis and identified the prognostic factors to assist clinicians considering extended AHT.Patients and MethodsPatients newly referred to the BC Cancer Agency with stage I to III estrogen receptor-positive BC diagnosed from 1989 to 2004 who had undergone AHT were identified by the BC Cancer Agency's Breast Cancer Outcomes Unit. Cases with recurrence, death, or contralateral BC occurring within the first 5 years were excluded. The 10-year event-free survival (EFS) and 95% confidence intervals (CIs) were calculated using the Kaplan-Meier method. This provided estimates of recurrence risk after the fifth year following the diagnosis. The histopathologic and age variables were examined for prognostic value by univariate analysis.ResultsWithin our cohort, 6615 women were postmenopausal and 1886 were premenopausal at the BC diagnosis. The median follow-up period was 11 years. The 10-year EFS for women aged < 50 years with stage I, II, and III disease was 94.8% (95% CI, 92.8%-96.3%), 88.3% (95% CI, 86.0%-90.2%), and 80.4% (95% CI, 73.6%-85.6%), respectively. Among women aged ≥ 50 years, the corresponding EFS rates were 94.8% (95% CI, 93.8%-95.6%), 86.3% (95% CI, 85.0%-87.5%), and 73.8% (95% CI, 69.1%-77.8%). EFS varied significantly by grade. The 10-year recurrence risk was < 10% with stage I cancer (any grade) and for stage II (node-negative and node-positive), grade I cancer.ConclusionOur data have identified BCs associated with a very low recurrence risk 5 to 10 years after diagnosis, providing women with such cancers confidence about a decision to discontinue AHT after 5 years.