A Comparison of Individual and Group Motivational Interviewing in the Improvement of Medication Adherence in Prostate Cancer

Prostate cancer is the second leading cause of cancer deaths globally among men. Medication non-adherence remains problematic, leading to adverse outcomes. Motivational interviewing has shown promise in improving adherence across health conditions. Thus, the aim of this study was to evaluate the effectiveness of motivational interviewing as an intervention to enhance medication adherence among patients diagnosed with prostate cancer.

In this randomized controlled trial, 161 men with prostate cancer in Iraq were allocated to individual motivational interviewing (n = 54), group motivational interviewing (n = 53), or the control group (n = 54). Medication adherence was assessed at baseline and after 10 weeks using the validated 8-item Morisky Medication Adherence Scale (MMAS-8). The interventions consisted of 10 weekly 45-60 minute motivational interviewing sessions focused on identifying motivations, barriers, and solutions to improve adherence. In this study, we employed a one-way analysis of variance (ANOVA) to assess the differences in pretest scores across the three groups, and analysis of covariance (ANCOVA) to compare medication adherence in the pretest and posttest phases. PASS 2023 software was used for sample size determination and SPSS software for the statistical analyses.

Medication adherence significantly improved in both the individual motivational interviewing (mean MMAS-8 score increased from 7.53 ± 2.76 to 8.61 ± 3.93) and group motivational interviewing (MMAS-8 ‎score increased from 4.88 ± 2.76 to 7.60 ± 3.45), compared to the control group (MMAS-8 ‎score ‎decreased from 5.00 ± 2.76 to 3.80 ± 2.24) (p = 0.002). The effect size was 0.244 with 0.869 statistical power. No significant difference was found between individual and group motivational interviewing.

This rigorously conducted randomized controlled trial provides strong evidence that motivational interviewing delivered individually or in groups effectively enhances medication adherence in prostate cancer patients. With medication non-adherence being a major barrier to optimal outcomes, oncology providers should strongly consider integrating motivational interviewing approaches to improve adherence behaviors. Future research can explore optimal implementation and long-term sustainability.