RESUMO
BACKGROUND: Breast cancer is one of the most common forms of cancer in the United States, with approximately 10% of newly diagnosed patients presenting with metastatic disease. Limited therapy options make the successful treatment of metastatic breast cancer (MBC) difficult. Current treatment options include drugs belonging to the classes of anthracyclines and taxanes as well as the drug capecitabine. Resistance to these classes of drugs is often acquired, thus highlighting the need for newer agents capable of managing treatment resistant disease. Ixabepilone is an antineoplastic agent from the epothilone class that was FDA-approved in October 2007 for the treatment of metastatic or locally advanced breast cancer. The FDA-approved indications for ixabepilone specify (a) use of ixabepilone in combination with capecitabine for the treatment of patients with metastatic or locally advanced breast cancer after (resistance to) treatment with an anthracycline and a taxane, or whose cancer is taxane resistant and for whom further anthracycline therapy is contraindicated; and (b) ixabepilone as a monotherapy for the treatment of metastatic or locally advanced breast cancer in patients whose tumors are resistant or refractory to an anthracycline, a taxane, and capecitabine. OBJECTIVES: To estimate the 3-year projected impact on the annual pharmacy budget for a hypothetical 1 million-member commercial plan that introduces and reimburses ixabepilone therapy for its FDA-approved indications: either as a monotherapy for patients pretreated with combined anthracyclines, taxanes, and capecitabine (ATC-p) or in combination with capecitabine for patients pretreated with anthracyclines and taxanes (AT-p). METHODS: U.S. prevalence and treatment data for MBC patients were obtained from published and nonpublished sources. The MBC population was stratified into AT-p and ATC-p populations. These 2 groups comprised the assumed study population. The model considered 2 scenarios-without (pre) and with (post) ixabepilone, either as monotherapy for ATC-p or combination therapy with capecitabine for AT-p patients. Market share data for chemotherapeutic treatment options for MBC pre-ixabepilone and in the first year post-ixabepilone were obtained from nonpublished, proprietary, real-world drug utilization data collected by IntrinsiQ LLC (Waltham, MA), for 2007 and 2008, respectively. Market shares for the second and third years post-ixabepilone were forecasted by the study authors based on IntrinsiQ data collected from January 2008 to January 2009 and the observed switching patterns in the 2007 and 2008 IntrinsiQ data. Drug costs were based on First DataBank Inc. Wholesale Acquisition Cost (accessed March 2009). The results for each indication were analyzed individually and summed to reflect the total impact of ixabepilone. Results were also considered on a per member per month (PMPM) basis to examine the relative impact on the plan. Sensitivity of the results to model assumptions was tested using univariate sensitivity analyses on the prevalence of AT-p and ATC-p, the price of ixabepilone, the price of comparator medications, and the ixabepilone market uptake. A key assumption was that ixabepilone would be used only in accordance with its current labeled indications. RESULTS: In a health plan population of 1 million members, the estimated number of female patients aged 20 years or older with recurrent MBC and previous treatment with either AT or ATC was 15 over the 3-year time horizon used in this budget impact model. For AT-p patients, the estimated incremental cost PMPM was $0.002 for each of the 3 years. The estimated incremental cost PMPM for the ATC-p population was $0.003 for year 1 and $0.004 for both year 2 and year 3. In sensitivity analyses, the PMPM impact varied between -$0.01 and $0.02 over the 3-year period. The model was most sensitive to the cost of ixabepilone. CONCLUSION: Given the poor prognosis and limited number of treatment options for patients with MBC, the need for widespread coverage of ixabepilone in accordance with FDA-approved indications can clearly be established. Assuming that ixabepilone is used only for its currently labeled indications, both the number of patients eligible for ixabepilone treatment and the expected budget impact of covering ixabepilone for this group of patients are relatively small.