Assessment of Adherence to Imatinib and Health-Related Quality of Life Among Patients with Gastrointestinal Stromal Tumor: A Cross-Sectional Study in an Oncology Clinic in Malaysia

PURPOSE: To evaluate the rate and predictors of non-adherence to imatinib in gastrointestinal stromal tumor (GIST) patients, as well as to compare the difference in health-related quality of life (HRQOL) between adherent and non-adherent patients. PATIENTS AND METHODS: A cross-sectional study at the Oncology Clinic, Hospital Kuala Lumpur was conducted from March to August 2018. All patients with metastatic and/or unresectable GIST aged ≥18 years old and on at least 3 months of imatinib were included. Adherence to imatinib was assessed using the 10-item validated Medication Compliance Questionnaire, with a score of <100% indicating non-adherence. Non-adherence predictors were determined by multiple logistic regressions. HRQOL was evaluated by the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 (EORTC QLQ-C30). The difference in the mean HRQOL scores between adherent and non-adherent groups was determined by multivariate analysis of variance. RESULTS: A total of 89 patients were enrolled, of which 49 (55.1%) were considered non-adherent. The significant predictors of non-adherence were age (adjusted odds ratio [OR] 0.93; CI 0.89–0.98; P = 0.007), presence of nausea and vomiting (OR 5.63; CI 1.25–25.27; P = 0.024), and presence of comorbidities (OR 4.56; CI 1.44–14.40; P = 0.010). Patients who were in the adherent group showed significantly better score in overall HRQOL, F (15, 73) = 2.09, P < 0.02; Pillai’s trace = 0.3, partial eta squared = 0.30. CONCLUSION: Non-adherence to long-term treatment with imatinib among patients with GIST should not be underestimated. Significant predictors of non-adherence among this population are younger age, presence of nausea and vomiting, as well as comorbidities. Patients with good adherence portrayed better HRQOL.