The impact of multiple pharmacy use on medication adherence in individuals with colorectal cancer.
Authors: Barnett Timothy , Rutter Cliff , Zaidi Shehla , Avalos-Reyes Elisea , McAuliff Kelly , Grover Rashmi , Feczko Lucia , Cavers William , Johnson Kjel Andrew 
Published: June 2024

11041 Background: Colorectal cancer (CRC) is the third most common cancer diagnosed in the US. The pharmacological care of older and often comorbid members with CRC is a growing healthcare issue. Cancer members are prone to the unintended consequences of multiple pharmacy use, as they often receive chemotherapy and symptom-relieving agents, in addition to medications they may be taking for other comorbidities. The purpose of this study was to assess multiple pharmacy use and adherence in a cohort of individuals with CRC. Methods: Adult pharmacy benefit manager (PBM) members who had at least 2 fills of either regorafenib, encorafenib, or trifluridine + tipiracil at specialty pharmacies between 1/1/2022 and 12/31/2022 were included. Any fills must have included one of the following diagnosis codes: C18.X, C19.X, C20.X, C21.8, C78.5, C78.6, D37.4, D37.5. Members were excluded if they did not maintain continuous eligibility for the 180 days prior to initiation in the study. Specialty pharmacy type included CVS Specialty, Competitor Specialty and Competitor non-specialty. Multiple pharmacy use was defined as utilizing more than one pharmacy for medication fills. The primary outcome was adherence determined by the medication possession ratio (MPR), defined as the number of days supplied/number of days in the evaluation period; optimal adherence was defined as MPR ≥ 0.8. Continuous and categorical variables were assessed with standard statistical tests. Bivariate logistic regression models were constructed for each covariate; significant variables were included in the multivariate model. Odds ratios (OR) and 95% confidence intervals (CI) are presented; p values < 0.05 were significant. Results: 891 members met all inclusion criteria; 362 (40.6%) met the definition of multiple pharmacy use. Members were on average 59.6 ± 11.2 years old and 54.3% were male. No differences in member demographics between specialty pharmacy type were found (all p > 0.05). Adherence was high with 79.5% of members having a MPR ≥ 0.8. Members with multiple pharmacy use had significantly lower adherence rates (76.0% vs. 81.9%; p=0.04) and MPRs (mean ± SD) (1.06 ± 0.45 vs. 1.15 ± 0.53; p=0.011). Controlling for specialty pharmacy type, medication used, and gender, multiple pharmacy use was significantly associated with decreased likelihood of optimal adherence compared to single pharmacy use (OR [95% CI]: 0.705 [0.507-0.98]; p= 0.038). Male gender was associated with significantly higher likelihood of optimal adherence (OR [95% CI]: 1.517 [1.093-2.107]; p=0.013). Conclusions: In this study of individuals with CRC receiving regorafenib, encorafenib, or trifluridine + tipiracil, utilizing multiple pharmacies for non-CRC medications was associated with a 29.5% decreased likelihood of optimal adherence compared to those who only utilized one pharmacy. Further examinations are warranted that include other modulators of adherence.