Nonadherence to imatinib treatment in patients with gastrointestinal stromal tumors: the ADAGIO study.

AIM To determine imatinib nonadherence rates in patients with gastrointestinal tumors (GIST) over 90 days. PATIENTS AND METHODS A prospective 90-day observational, open-label, multicenter study was carried out of 28 evaluable GIST patients on imatinib. Nonadherence behavior was measured using a 4-item patient interview. Clinicians, patients, and collaterals rated perceived patient adherence on a 0-100 VAS scale. RESULTS Nonadherence rates in the 4 weeks prior to baseline and follow-up were 29% (95% CI=26-32) and 24% (95% CI=21-27, p>0.05). Mean VAS ratings of perceived adherence ranged from 95.2 ± 10.2 to 97.3 ± 4.8 (p>0.05 for time and source of rating). Correlations between perceptions of and actual adherence behavior were negative. CONCLUSION In this first study on imatinib nonadherence in GIST patients, rates were similar to those observed in patients with chronic myeloid leukemia, higher than clinically expected and exceeding meta-analytic estimates for cancer. Nonadherence rates were consistent across the 90-day period. Nonadherence behavior should be assessed by clinicians.