OBJECTIVES: A cancer diagnosis may affect the management of other comorbid chronic conditions. An evaluation of change in adherence to medications for these conditions after a cancer diagnosis may help in understanding the effect of cancer. This study aims to summarize existing literature assessing the impact of cancer diagnosis on adherence to medications for non-cancer chronic conditions.
METHODS: This systematic review was performed using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement. PubMed, EMBASE, and all databases of Web of Science were searched through February 2022 using the terms “change” and “chronic” and “medication” and “adherence” and “after” and “cancer diagnosis”. References of included studies were also manually searched. Studies were included if they were retrospective cohort studies in which cancer diagnosis was the exposure, and adherence to non-cancer chronic disease medications before and after cancer was one of the outcomes. At least two investigators independently determined the eligibility of studies.
RESULTS: This study identified sixty-five published articles. Eleven studies published between 2013 and 2021 were included based on the inclusion and exclusion criteria. The most commonly studied type of cancer was breast cancer (n=11 [100.00%]), followed by colorectal cancer (n=6 [54.55%]). The most evaluated class of medications for non-cancer chronic conditions were antidiabetics (n=7 [63.64%]) and antihyperlipidemics (statins) (n=7[63.64%]), followed by antihypertensives (n=5 [45.45%]). The types of statistical analysis techniques used varied substantially, with difference-in-differences being the most preferred (n=4 [33.33%]). Overall, the majority of studies (n=10 [90.91%]) reported some decline in medication adherence after a cancer diagnosis.
CONCLUSIONS: This systematic literature review confirms the high medication nonadherence burden that exists in cancer patients with comorbid chronic conditions. It is important that interventions are planned, in accordance with practice guidelines, to routinely monitor and improve adherence to non-cancer comorbid conditions, which may invariably have a significant impact on cancer outcomes.
