Abstract P2-14-07: Evaluation of Aromatase Inhibitor failure and total healthcare expenditures among post-menopausal women with metastatic ER+/HER2− breast cancer in the US
Authors: Namjoshi M , Landsman-Blumberg P , Thomson E , Chu BC 
Published: August 2014

Aromatase Inhibitors (AIs) have replaced tamoxifen as first-line therapy for post-menopausal women with metastatic, ER+ breast cancer (BC). However, little information is available on the real-world use of AIs. This retrospective administrative claims study compared healthcare expenditures of post-menopausal women with metastatic ER+/HER2− BC treated with AIs and experiencing 0 or ≥ 1 AI failures (AIF).

Women ≥ 55 years of age newly diagnosed with stage IV BC (index) were identified in the 2006–2010 Thomson Reuters MarketScan databases and followed until the earliest of chemotherapy, combination therapy, end of enrollment, or end of study (03/31/2011). ER+/HER2− disease was defined as any endocrine therapy (ET: tamoxifen, fulvestrant) or AI (anastrozole, letrozole, or exemestane) use and no trastuzumab, lapatinib or toremifene use anytime in the 6-month pre-or variable length post-index periods. Those with post-index AI use except where use followed chemotherapy or combination therapy were retained for analysis. AIF post-index was defined as a switch to an alternative AI, ET, chemotherapy, or combination therapy. All-cause healthcare expenditures, defined as total provider payments (insurer + patient + COB) were examined by type of service and in total, and expressed as per patient per month (PPPM). A series of log-gamma regressions were used to examine the relationship between AIF and PPPM expenditures as a form of cost ratios (CRs), adjusting for potential confounding factors such as patient demographic and clinical characteristics.

Among 4,249 eligible patients, 36% had ≥1 AIF. At index, AIF patients were more likely to have liver (8% vs. 5%), lung (11% vs. 8%), and bone metastases (60% vs. 49%), all p &lt; 0.01; as likely to have brain metastases (6.5% vs. 6.6%, p = 0.880); and less likely to have metastases to other sites (39% vs. 48%, p &lt; 0.001). Median days of follow-up were 395 for AIF and 466 for no AIF patients. Post-index, patients with AIF had significantly higher total unadjusted PPPM healthcare expenditures ($6507 vs. $3974), and across all service types including inpatient stays ($2529 vs. $1369), radiation treatments ($465 vs. $238), diagnostic radiology ($889 vs. $599), laboratory tests ($333 vs. $196), and other non-office visit outpatient services ($1546 vs. $932), all p &lt; 0.001. Regression analysis showed that metastases to the lung (CR 1.32 CI: 1.17–1.50), brain (CR 1.76, CI: 1.54–2.01), liver (CR 1.96 CI: 1.67–2.30), bone (CR 1.53 CI: 1.40–1.68), and other sites (CR 1.41 CI: 1.29–1.55) at diagnosis significantly increased PPPM expenditures compared to having metastases at another site while controlling for AIF status and other confounders, while AIF also significantly increased costs (CR 1.50 CI: 1.39–1.61). Using the bootstrap approach, incremental adjusted PPPM costs in women with AIF relative to those with no AIF was estimated at $2051 (CI: $1666-$2426, p &lt; 0.001).

In real world practice, almost 40% of women with ER+/HER2− metastatic BC treated with AIs failed at least 1. AIF was associated with expenditures 50% higher than patients with no AIF. Furthermore, substantial costs were associated with metastases regardless of the site.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P2-14-07.