PURPOSE. The Breast Cancer Prevention Trial demonstrated that tamoxifen (tam) effectively reduces breast cancer risk in women. However, tam's side-effect profile has severely constrained its use. For tam, contralateral breast cancer rates have accurately reflected its primary prevention effect. A recent breast cancer report (N = 6186) demonstrated that anastrazole reduces cancer occurrence in the contralateral breast 48% more than tam and has less adverse effects. This report from the Arimidex, Tamoxifen Alone or in Combination Trialists' Group (ATAC), involved 68 months of follow-up and suggests that anastrazole is a good option for primary breast cancer prevention. However, the use of anastrazole might be limited by its high price. Therefore, the purpose of our study is to evaluate the probable cost-effectiveness of anastrazole for primary, chemoprevention.

METHODS. We performed decision analysis using a Markov model. Cost-effectiveness is reported from the payor's perspective. Patient characteristics and the annual rates of breast cancer, stroke, venous thrombo-embolic disease, endometrial cancer, and fracture were derived from the Breast Cancer Prevention Trial of the National Surgical Adjuvant Breast and Bowel P-1 Project (NSABBP) and the ATAC group. Utility scores were measured by questioning 106 women. Sensitivity analysis was performed.

RESULTS. Using the 3.4%, 5-yr average breast cancer risk in the NSABBP combined with contralateral breast cancer data from ATAC, we determined that anastrazole increases quality-adjusted life (QAL) compared to no treatment for high-risk women aged 50 to 65 years. The cost per QALY gained ranged from $33,110 for the women aged 50-55 to $73,500 at age 65. Sensitivity analysis revealed that the utility score for breast cancer, the probability of stroke, and the cost of anastrazole influence cost-effectiveness. Incremental QAL gains of anastrazole over tam were obtained at the cost of $18620 per QALY at age 50 and $41,700 at age 65. This model was only sensitive to the price of anastraloze, utility of breast cancer, and breast cancer risk reduction of anastrazole relative to tam. If the anastrazole price (current cost $225/month) is lowered to $138/month for 50 yr olds, tam is dominated.

CONCLUSION. For high-risk women aged 50-65, we anticipate anastrozole to be a cost-effective alternative for breast cancer prevention. If anastrazole were available at a moderate price reduction, the anastrazole chemoprevention strategy would be dominant over tam.