Assistant Professor Massachusetts College of Pharmacy, Massachusetts, United States
Background: Cancer diagnoses can challenge the management of chronic co-morbid conditions, yet the longitudinal patterns and factors associated with treatment disruptions following cancer diagnosis remain poorly characterized.
Objectives: To evaluate disruptions in Type 2 Diabetes Mellitus (T2DM) treatment, including adherence, regimen changes, discontinuations, and sequencing, following colorectal cancer (CRC) diagnosis in elderly U.S. patients.
Methods: Using the SEER-Medicare (2015-2019) database, we conducted a retrospective cohort study of patients aged 66 and older who were receiving treatment for preexisting T2DM at the time of CRC diagnosis. Patients were required to have continuous Medicare Parts A, B, and D coverage throughout the analysis period. We assessed treatment adherence using medication possession ratios (MPR), comparing adherence in the year before and after CRC diagnosis. Kaplan-Meier estimates, Logistic and Cox models were used to evaluate the timing and correlates of treatment changes and discontinuation. Additionally, we characterized treatment sequencing during the first year following CRC diagnosis.
Results: A total of 2,989 patients met the eligibility criteria (51.5% female, mean age: 76.9 years [SD: 7.2]). At CRC diagnosis, 37.2% were on multiple T2DM drug classes, with metformin being the most commonly prescribed (57.3%). Majority of patients reported declines in adherence to T2DM treatment post-CRC with greater declines among surgical patients, those with Stage IV CRC, and higher comorbidity burdens (p ≤ 0.05). Nearly half (47.4%) modified their regimens, with those on metformin (adj. OR: 0.75 [95% CI: 0.61–0.91]) or single-drug therapies (adj. OR: 0.06 [95% CI: 0.05–0.08]) being less likely to change treatments (25th percentile survival time: 286 days for single agent users vs. 34 days for patients on multiple classes). Early discontinuation was uncommon (5.3%), but more likely among patients with complex regimens (adj. HR: 2.09 [95% CI: 1.41–3.09]) and those receiving CRC-directed surgery (adj. HR: 2.24 [95% CI: 1.34–3.78]). Treatment sequencing showed substantial variation, with a general shift toward regimen simplification.
Conclusions: CRC diagnosis significantly disrupts T2DM treatment, often leading to less intensive regimens. Further research is needed to evaluate the clinical implications of these treatment changes on patient outcomes.
