[4044] Adherence with adjuvant anastrozole therapy among women with early stage breast cancer.

Partridge AH, LaFountain A, Taylor B, Asnis-Alibozek A.. Dana-Farber Cancer Institute, Boston, MA; AstraZeneca Pharmaceuticals, Wilmington, DE

Background: Available research suggests that many patients with chronic disease are non-adherent with prescribed medication regimens. Limited studies evaluating adherence with tamoxifen (T) among women with early stage breast cancer have revealed adherence estimates ranging from 25% to 96%. The largest study of adherence to T using a retrospective claims database found that adherence declined substantially over time, despite clinical trial evidence suggesting 5 years of T yields a 50% reduction in breast cancer recurrence. Recent studies have shown anastrozole (A) provides additional benefit for post-menopausal women with hormone receptor-positive early stage breast cancer. No previous studies have focused on adherence with aromatase inhibitors. Methods: We used longitudinal claims data from a large national commercial health plan to estimate adherence with adjuvant A therapy among women with early breast cancer who had initiated A therapy between January 2002 and March 2004. For a subset of patients, 36 months of follow-up information was available, through November 2005. We developed an algorithm using procedural and diagnostic codes to identify women with early stage breast cancer. Persistency was defined as the percentage of patients continuously filling prescriptions month-by-month over time. Adherence was defined as the proportion of days that patients had medication available over the observation period (i.e., days covered). Women who had less than 80% days covered over their first 12 months of therapy were defined as non-adherent, and were further analyzed to determine their patterns of persistence. All analyses were replicated using claims data from another large closed health system. Results: 1,859 women in the database were found to have new anastrozole prescription claims during the period of study. Using our algorithm, 1,498 of these women were classified as having early stage breast cancer. Persistency analysis of the 1,498 women revealed that 85% were still filling prescriptions by month 12. For women with at least 12 months of continuous eligibility in the health plan (n = 1,111), the mean days covered over the first 12 months of therapy was 88%. 19% of these women had less than 80% of days covered and were considered non-adherent. For women with 36 months of continuous eligibility (n=158), the mean number of days covered in year 1 was 86%, year 2 was 82% and year 3 was 79%. 22% of this subset of women were considered non-adherent in year 1, increasing to 32% in year 3. Data from the replication analysis will be presented.Conclusions: One in five women with early stage breast cancer may be sub-optimally adherent with adjuvant A therapy during the first year of treatment. These findings are consistent with studies evaluating adherence with adjuvant T therapy. Clinicians who care for women with early stage breast cancer should be aware that adherence with hormonal therapy may be a problem.

Saturday, December 16, 2006 7:00 AM

Poster Session IV: Treatment: Endocrine Therapy (7:00 AM-9:00 AM)