Anastrozole is cost-effective vs tamoxifen as initial adjuvant therapy in early breast cancer: Canadian perspectives on the ATAC completed-treatment analysis.
OBJECTIVE
To conduct an economic analysis comparing tamoxifen and anastrozole (Arimidex) in the adjuvant treatment of hormone receptor-positive (HR+), post-menopausal early breast cancer patients.


METHODS
An economic model examined typical patients (64 years of age, HR+, 64% node negative) from the Arimidex, tamoxifen alone, or in combination (ATAC) trial over a lifetime horizon. Rates of events were derived from ATAC trial results. Post-trial event rates were drawn from the literature for tamoxifen; event rates for anastrozole were modified by the relative risks observed in the ATAC trial. Resource utilization was drawn from Statistics Canada's Population Health Model for breast cancer, supplemented by an expert panel. A public health care system perspective, 2004 Canadian prices and a 5% discount rate were employed.


RESULTS
Anastrozole-taking patients incurred additional hormonal treatment costs compared to tamoxifen-taking patients (incremental lifetime cost, 6,974 Canadian dollars per patient), partially offset by reduced downstream recurrences of breast cancer (1,143 Canadian dollars lifetime savings per patient) for a net incremental cost of 5,796 Canadian dollars per patient on anastrozole. The anastrozole-treated patients were projected to experience a 5.6% absolute risk reduction of first breast cancer recurrence and a 2.8% absolute risk reduction in breast cancer death. This corresponded to 30,000 Canadian dollars per life year gained and 28,000 Canadian dollars per quality-adjusted life year gained (95% confidence interval, 17,428 to 54,605 Canadian dollars). The results were affected by the duration and extent of anastrozole benefit under sensitivity analysis but remained cost-effective.


CONCLUSIONS
Compared to tamoxifen, anastrozole therapy is effective and cost-effective as initial adjuvant therapy in post-menopausal, HR+ early breast cancer patients.
Rocchi
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Axia Research, Hamilton, Canada. angela@axiaresearch.com
Verma
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D000704:Analysis of Variance; D000077384:Anastrozole; D018931:Antineoplastic Agents, Hormonal / Q000008:administration & dosage / Q000191:economics; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000191:economics* / Q000627:therapeutic use*; D047072:Aromatase Inhibitors / Q000008:administration & dosage / Q000191:economics; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000191:economics* / Q000401:mortality; D002170:Canada; D017024:Chemotherapy, Adjuvant; D003362:Cost-Benefit Analysis; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D009364:Neoplasm Recurrence, Local / Q000517:prevention & control; D009570:Nitriles / Q000008:administration & dosage / Q000191:economics; D019057:Quality-Adjusted Life Years; D016032:Randomized Controlled Trials as Topic; D040242:Risk Reduction Behavior; D012680:Sensitivity and Specificity; D015996:Survival Rate; D013629:Tamoxifen / Q000008:administration & dosage / Q000191:economics; D013997:Time Factors; D016896:Treatment Outcome; D014230:Triazoles / Q000008:administration & dosage / Q000191:economics
D018931:Antineoplastic Agents, Hormonal; D047072:Aromatase Inhibitors; D009570:Nitriles; D014230:Triazoles; D013629:Tamoxifen; D000077384:Anastrozole