Adherence to mercaptopurine (6-MP) and habit strength in pediatric acute lymphoblastic leukemia (ALL).

person Mira Yang Department of Medical Education, Northwestern University Feinberg School of Medicine, Chicago, IL info_outline Mira Yang, Sherif Mohamed Badawy, Revika Singh, Kathryn King

Authors person Mira Yang Department of Medical Education, Northwestern University Feinberg School of Medicine, Chicago, IL info_outline Mira Yang, Sherif Mohamed Badawy, Revika Singh, Kathryn King Organizations Department of Medical Education, Northwestern University Feinberg School of Medicine, Chicago, IL, Division of Hematology, Oncology, and Stem Cell Transplant, Ann and Robert H Lurie Children's Hospital of Chicago, Chicago, IL, Division of Hematology, Oncology, and Stem Cell Transplant, Ann & Robert H. Lurie Children’s Hospital of Chicago, Chicago, IL Abstract Disclosures Research Funding No funding received None. Background: Rates of adherence to mercaptopurine (6-MP) below 90% have been associated with increased relapse in pediatric patients with acute lymphoblastic leukemia (ALL). Habit strength has been associated with medication adherence through multiple mechanisms, including self-efficacy and social norms. The goal of this study was to investigate the relationship between habit strength, adherence to 6-MP, and health-related quality of life domains. Methods: This was a single center, cross-sectional study. A total of 52 participants, including 11 patients (ages 12-23, mean age 16 ± 4, 45% Female) and 41 parents/caregivers (ages 25-43, mean age 37 ± 5, 80% Female) of patients with ALL under the age of 18. Participants completed the Visual Analogue Scale (VASdose), PROMIS Medication Adherence Scale (PMAS), Self-Regulated Habit Index (SRHI), and PROMIS quality of life measures (PROMIS-CAT). Spearman’s rho correlations were used to assess relationships between variables. Eleven semi-structured interviews of patients and caregivers were conducted and analyzed using Grounded Theory coding and thematic analysis. Results: Overall, 81% (n = 42/52) of participants surveyed had high adherence to 6-MP (VASdose ≥95%); 91% (n = 10/11) of patients and 78% (n = 32/41 of parents/caregivers reported high adherence. The median VASdose and PMAS score were 100% (IQR 97-100) and 39.5 (IQR 38-40) across all participants, respectively. Participants with higher adherence, VASdose ≥ 95% and PMAS ≥ 39.5, reported less physiological stress (p = 0.02), and better cognitive function (p = 0.09) and peer relations (p = 0.08), compared to those with lower adherence. No significant correlation was found between medication adherence rate and habit strength. Emerging themes from qualitative coding included the influence of routine and automaticity on 6-MP as well as adherence strategies. Strategies such as reminders, care team communication, and developing personalized tools were cited by participants as potentially improving adherence in taking or administering 6-MP. Other facilitating participant characteristics included experience with medication administration, self-efficacy, and access to social support. Financial burden, scheduling conflicts, and medication access were common barriers cited by participants. Conclusions: Nearly one-fifth of our participants reported lower adherence to 6-MP (VASdose < 95%), which increases risk of relapse. Medication adherence to 6-MP was not associated with habit strength, but our results show preliminary associations between adherence rates and quality of life outcomes, such as physiological stress. Behavioral interventions are needed to better optimize adherence to 6-MP and improve health outcomes in pediatric ALL.