Antidepressant adherence trajectory before cancer diagnosis and risk of antidepressant discontinuation after cancer diagnosis among middle-aged US adults.

e18890 Background: For middle-aged adults taking antidepressants before cancer diagnosis, concerns exist about drug-drug interactions between antidepressants and antineoplastics. Clinical guidelines recommend detailed assessment of the new cancer survivor's past history of antidepressant use before considering antidepressant discontinuation. We aimed to determine whether, in real-world settings, the risk of antidepressant discontinuation after cancer diagnosis is associated with survivors’ past antidepressant adherence trajectories. Methods: A retrospective cohort of 45 to 64-year old individuals with incident cancer diagnosis (index date) and ≥2 antidepressant fills in the 9 months before index date, IQVIA PharMetrics Plus for Academics claims, 2006-2020. Antidepressant adherence in the 9-month baseline was measured as monthly proportion of days covered (PDC) before tamoxifen initiation. Group-based trajectory modeling (GBTM) was used to identify clusters of survivors with distinct antidepressant adherence trajectories pre-index date i.e., we calculated polynomial functions of monthly PDCs and compared 2 to 6-group finite mixture models to determine which model best fit the data, based on the Bayesian Information Criterion, expert-adjudged parsimony and ≥10% of the sample in each trajectory group. Antidepressant discontinuation after cancer diagnosis was defined as a 45-day gap in antidepressant supply. Survivors were censored at first of either antidepressant discontinuation, loss of enrollment or 1 year post-index date. Cox regression compared the hazard of antidepressant discontinuation by trajectory group, adjusted for demographics, mental disorder and cancer type. Results: We identified 7,293 middle-aged cancer survivors with prior antidepressant use; females 72%, mean age (SD) 56 (7) years. GBTM identified 4 adherence trajectory groups (consistently high, steady increase, declining, and recent start); metastatic cancer being characteristic of the latter 3 groups relative to the consistently high group. Antidepressant discontinuation was lowest in the consistently high group (26% [mean months-to-discontinuation: 9]) and highest in the declining (68% [5]) and recent start (51% [6]) groups, p < .01. Hazard ratios [95% CI] of discontinuation were significantly higher in the declining (2.7 [2.3 – 3.2]), recent start (1.9 [1.7 – 2.0]) and steady increase (1.5 [1.4 – 1.6]) groups, relative to the consistently high group. Conclusions: Middle-aged cancer survivors with past trajectories of consistently high adherence to antidepressants experience lower risk of antidepressant discontinuation after cancer diagnosis in real-world practice. However, concern remains about the unintended health outcomes of relatively higher antidepressant discontinuation among survivors diagnosed with metastatic cancer.