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.