Identifying breast cancer patients most likely to benefit from aromatase inhibitor therapy after adjuvant tamoxifen

BACKGROUND. The purpose of the current study was to examine patient selection for an aromatase inhibitor in breast cancer patients who were free from adverse events 5 years after treatment with tamoxifen. METHODS. In all, 471 women were treated with breast-conserving surgery, axillary lymph node dissection, and radiation. Eligibility included T1-2 disease, tamoxifen use, follow-up of >= 5 years, no prior breast cancer, and freedom from all events at 5 years of follow-up. Patients treated with chemotherapy more often had T2 disease and positive lymph nodes, and were aged < 60 years compared with patients treated with tamoxifen alone. No patient during the period of the current study (1982-1999) received an aromatase inhibitor. The median follow-up was 8.25 years. RESULTS. There were 36 events: 10 contralateral breast cancers (CBCs) and 26 recurrences (8 local, I regional, and 17 distant). The 10-year risk of locoregional recurrence was 2.5%, the 10-year risk of CBC was 3.6%, and the 10-year risk of distant metastasis was 4.4%. The event-free survival rate for all patients was 93%. Only >= 4 positive lymph nodes and premenopausal status were found to be independent variables for decreased event-free survival on multivariate analysis. The overall survival rate was 89%. Only younger age and lower lymph node status were found to be significant predictors of improved overall survival. CONCLUSIONS. In the current study, a 40% reduction in recurrence/CBC with the addition of an aromatase inhibitor after 5 years of tamoxifen treatment would have had a marginal benefit of 1% to 2%. Women who were premenopausal and patients with >= 4 positive lymph nodes would have the greatest absolute benefit of > 3% in the 10-year event-free survival rate from extended therapy. The decision needs to be individualized for patients aged >= 60 years based on their initial lymph node status and the presence of comorbidities that could lower their 5-year life expectancy.