Relationship between compliance with imatinib mesylate and medical costs for patients with CML and GIST

Abstract

6618 Background: Imatinib mesylate, an oral tyrosine kinase inhibitor for treatment of chronic myeloid leukemia (CML) and gastrointestinal stromal tumors (GIST), has been found both effective and cost-effective. This study examines the relationship between imatinib compliance and health care costs for patients (pts) with CML and GIST. Methods: This retrospective study used claims data from a large national US health plan. Pts had =2 imatinib claims from 6/1/01–3/31/05; =1-year follow-up after the 1st imatinib claim; and diagnosis of CML (ICD9 205.1x) or GIST (ICD9 159.0, 159.8, 159.9 or evaluation of claims and attribution of GIST by independent hematologist/oncologist). Compliance was measured with a medication possession ratio ((days of imatinib during follow-up / days of follow- up)*100). Compliance categories were good, =90%; medium, 70–89.9%; poor, <70%. Total follow-up medical and health care (medical + pharmacy) costs were measured and compared across compliance categories; t-tests compared mean costs. Results: 374 CML and 91 GIST pts had mean age of 52.1 ± 14.0 years. 274 (59%) pts were male. 234 (50%) of pts had 12–24 months follow-up; 231 (50%) had 25–57 months. Mean and median compliance across all pts were 69.4% and 79.7%, respectively. 122 (33%) CML and 32 (35%) GIST pts had good compliance; 149 (40%) CML and 42 (46%) GIST pts had poor compliance. Mean medical costs across all pts were lower and less variable with good compliance ($22,882 ± 22,791) than with medium ($40,366 ± 68,186), p=0.007) and poor ($104,961 ± 190,559), p<0.001). Similarly, mean medical costs for CML pts with good, medium, and poor compliance were $21,456 (±22,127), $41,537 (±72,238, p=0.008), and $117,004 (±211,292, p<0.001), respectively. Mean medical costs for GIST pts were: good=$28,318 (±24,781); medium=$33,270 (±35,356, p=0.584); and poor=$62,235 (±68,751, p<0.001). Mean total health care costs were 21.7% lower for pts with good compliance relative to those with poor. Conclusions: Good imatinib compliance was associated with significantly lower medical costs. Mean total medical costs were 78% lower with good compliance relative to poor. Compliance is an important treatment issue for both clinical and medical cost outcomes. No significant financial relationships to disclose.