Antidepressant adherence and breast cancer recurrence risk in women with major depressive disorder: a retrospective cohort.

BACKGROUND

Women with major depressive disorder (MDD) who develop breast cancer have higher breast cancer recurrence compared with women without MDD. The reason for the higher recurrence is hypothesized to be multifactorial. We sought to determine whether nonadherence to antidepressants is associated with increased recurrence among women with MDD and breast cancer.

METHODS

We established a retrospective cohort of 6051 women (aged ≥ 18 years), with and without MDD, who were diagnosed with early-stage invasive breast cancer between 2010 and 2019 with follow-up through 2022 using medical record data from the United States Veterans Affairs Healthcare System. We assessed antidepressant adherence in women with MDD more than 2 years before breast cancer diagnosis. We evaluated multiple adherence thresholds (proportion of medication days covered), ranging from ≥20% to 100%. We used multivariable competing-risks regression to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the statistical interaction between MDD and antidepressant adherence on recurrence, adjusting for sociodemographic, clinical, and prognostic factors.

RESULTS

Among women with MDD and breast cancer (N = 1754), 94% initiated an antidepressant. A threshold of 60% was the minimum adherence level for there to be a statistically meaningful difference in recurrence between nonadherent and adherent women with MDD. Thirty-nine percent were nonadherent at this threshold. The association between MDD and recurrence was highest among women who did not use antidepressants (HR = 2.20, 95% CI = 1.54 to 3.15), followed by women who were nonadherent (HR = 1.52, 95% CI = 1.24 to 1.86), and lowest among women who were adherent (HR = 1.19, 95% CI = 0.99 to 1.42).

CONCLUSION

Adherence to antidepressants could potentially reduce recurrence in patients with breast cancer and MDD.