LONG-TERM MEDICAL COSTS OF ADJUVANT ENDOCRINE THERAPY FOR EARLY BREAST CANCER: A POPULATION-BASED STUDY

Purpose: To estimate total resource utilization and health care costs attributable to adjuvant endocrine therapy for early stage breast cancer (EBC) patients 65 years and older in Ontario, Canada in 2001-2008 from the health care payer’s perspective.  Describing the cost of care for these patients is useful to understand the economic burden of illness, explore patterns of care, and provide reliable data for economic studies.

Method: As convincing data for monotherapy with an Aromatase Inhibitor (AI) has recently demonstrated improved disease-free survival over Tamoxifen for hormone-sensitive EBC in large randomized clinical trials, and as Anastrozole is the AI in longest use, this study examined the economic impact of the incorporation of monotherapy with Anastrozole into the treatment of EBC.  Direct medical resource utilization data were identified using linked administrative data: hormonal drug therapy, physician consultation, procedures conducted, adverse events.  Costs (in $Canadian, 2009) were determined from the literature and applied to all resource utilization data.     

Result:  In 2001-2008, a total of 4489 cases of female EBC aged ≥65 years received five years of Tamoxifen monotherapy, and 5048 cases received five years of Anastrozole monotherapy.  As expected, average drug cost per case was significantly higher for Anastrozole than Tamoxifen ($5459 vs. $659, p<0.0001).  The mean cost for health-care resource use was significantly higher for cases receiving Anastrozole: physicians’ billing for chemotherapy ($440 for Anastrozole vs. $347 for Tamoxifen, p<0.0001), for radiotherapy ($847 for Anastrozole vs. $718 for Tamoxifen, p<0.0001), for surgical interventions ($13581 for Anastrozole vs. $10719 for Tamoxifen, p<0.0001), and for medical follow-up visits ($1067 for Anastrozole vs. $1005 for Tamoxifen, p<0.0001).  With the exception of hip fracture, ($32749 for Anastrozole vs. $34627 for Tamoxifen, p=0.01), no significant difference was found in treating adverse events due to endocrine therapy of EBC: acute myocardial infarction ($10782 for Anastrozole vs. $11347 for Tamoxifen, pNS), stroke ($56480 for Anastrozole vs. $59435 for Tamoxifen, pNS), venous thromboembolism ($5513 for Anastrozole vs. $5568 for Tamoxifen, pNS), and wrist fracture ($416 for Anastrozole vs. $387 for Tamoxifen, pNS).

Conclusion: Anastrozole-taking patients incurred additional hormonal treatment costs compared to Tamoxifen-taking patients, but this was offset by costs associated with adverse events.  Further research will explore the survival benefit associated with adjuvant endocrine therapy in the general population to derive estimates of cost-effectiveness.