6038 Background: Imatinib is an oral therapy with efficacy in chronic myelogenous leukemia (CML) and gastrointestinal stromal tumors (GIST). Optimal dosing and adherence to treatment is critical to achieve the best clinical outcomes. This study examined compliance and persistency with imatinib and identified the clinical and patient characteristics related to compliance.
METHODS
Claims data from a US health plan were used to identify imatinib-treated patients from 6/1/01-3/31/04 who had continuous pharmacy and medical benefits in the 3 months prior and 12 months following initiation of imatinib therapy, and a diagnosis of CML or GIST (ICD-9-CM 205.1, 205.10, or 205.11 for CML; 159.0, 159.8, or 159.9 for GIST). Compliance was defined by medication possession ratio (MPR = total days supply of imatinib in the first year divided by 365). Persistency was defined as failure to refill imatinib within 30 days from the run-out date of the prior prescription. Multivariate analyses were used to identify key factors associated with compliance.
RESULTS
Total 878 imatinib-treated patients were identified of whom 413 had at least 15 months' continuous eligibility. Sixty-nine percent (n = 286) were diagnosed with CML, 8% (n = 34) with GIST, and 23% (n = 93) with neither. Results are presented for CML and GIST patients. The average age was 51 and 58% were males. The average starting daily dose was 424 mg, with 80% (n = 255) initiating on 400 mg daily. The mean MPR was 76%. Overall, 28% patients discontinued imatinib for at least 30 consecutive days during the 1-year follow up period. Multivariate analyses indicated MPR improved with age until age 51 and then deteriorated (p < 0.001) but at a diminishing rate, decreased as the number of medications increased (p < 0.001), and was lower in women (p = 0.005) and patients with more cancer complications (p < 0.001). In addition, women were more likely to discontinue than men (OR = 2.08; p = 0.003).
CONCLUSIONS
Compliance to imatinib was about 75% with 30% of patients interrupting therapy for at least 30 consecutive days in the first year. It has been found that interruption of imatinib therapy may lead to rapid tumor progression in GIST (PASCO05 Le Cesne #9031). Not having patients take the correct doses on a regular basis may lead to sub therapeutical clinical outcomes. [Table: see text].