Use of antidepressants after colon cancer diagnosis and risk of recurrence.

Objective: Prior research examining the association between use of antidepressants after colon cancer diagnosis and risk of recurrence is scant. We evaluated this association among colon cancer patients diagnosed at two integrated health care delivery systems in the United States.

Methods: We conducted a cohort study of stage I to IIIA colon cancer patients diagnosed at greater than or equal to 18 years of age at Kaiser Permanente Colorado and Kaiser Permanente Washington during 1995 to 2014. We used pharmacy records to identify dispensings for antidepressants and tumor registry records and patients' medical charts to identify cancer recurrences. Using Cox proportional hazards models, we estimated the adjusted hazard ratio (HR) of colon cancer recurrence comparing patients who used antidepressants after diagnosis to those who did not. We also evaluated the risk associated with use of selective serotonin reuptake inhibitors (SSRIs) and tricyclic antidepressants (TCAs) separately.

Results: Among the 1923 eligible colon cancer patients, 807 (42%) used an antidepressant after diagnosis and 139 had a colon cancer recurrence during an average 5.6 years of follow-up. Use of antidepressants after colon cancer diagnosis was not associated with risk of recurrence (HR: 1.14; 95% confidence interval [CI], 0.69-1.87). The HR for use of SSRIs was 1.22 (95% CI, 0.64-2.30), and for TCAs, it was 1.18 (95% CI, 0.68-2.07).

Conclusions: Our findings suggest that use of antidepressants after colon cancer diagnosis was common and not associated with risk of recurrence. Future larger studies with greater power to examine risk associated with individual antidepressants would be valuable additions to the evidence base.