Changes in chronic medication adherence in older adults with cancer versus matched cancer-free cohorts

A cancer diagnosis can influence medication adherence for chronic conditions by shifting care priorities or reinforcing disease prevention. This study describes changes in adherence to medications for treating three common chronic conditions - diabetes, hyperlipidemia, and hypertension - among older adults newly diagnosed with non-metastatic breast, colorectal, lung, or prostate cancer.

We identified Medicare beneficiaries aged ≥66 years newly diagnosed with cancer and using medication for at least one chronic condition, and similar cohorts of matched individuals without cancer. To assess medication adherence, proportion of days covered (PDC) was measured in six-month windows starting six-months before through 24 months following cancer diagnosis or matched index date. Generalized estimating equations were used to estimate difference-in-differences (DID) comparing changes in PDCs across cohorts using the pre-diagnosis window as the referent. Analyses were run separately for each cancer type-chronic condition combination.

Across cancer types and non-cancer cohorts, adherence was highest for anti-hypertensives (90-92%) and lowest for statins (77-79%). In older adults with colorectal and lung cancer, adherence to anti-diabetics and statins declined post-diagnosis compared with the matched non-cancer cohorts, with estimates ranging from a DID of -2 to -4%. In older adults with breast and prostate cancer cohorts, changes in adherence for all medications were similar to non-cancer cohorts.

Our findings highlight variation in medication adherence by cancer type and chronic condition. As many older adults with early stage cancer eventually die from non-cancer causes, it is imperative that cancer survivorship interventions emphasize medication adherence for other chronic conditions.