Depressive disorders are common in women with breast cancer. Antidepressants are often prescribed not just for depression but also for symptoms like hot flashes related to tamoxifen treatment. Concern has been raised that antidepressants that interfere with the cytochrome P450 2D6 enzyme may decrease the conversion of tamoxifen to more active metabolites (J Clin Psychiatry 2009 Dec;70(12):1688). A new cohort study followed 2,430 women ? 66 years old with breast cancer who were taking both tamoxifen and a selective serotonin reuptake inhibitor (SSRI) antidepressant. There were 374 breast cancer-related deaths during a mean follow-up period of 2.4 years. Analyses were adjusted for multiple potential confounders including age, tamoxifen treatment duration, timing of initiation of tamoxifen to breast cancer, and comorbidities. As the proportion of time during which patients treated with tamoxifen were also treated with paroxetine (Paxil) increased, the risk of breast cancer-related death also increased (level 2 [mid-level] evidence). Risk of breast cancer death increased from 24% to 91% as concomitant paroxetine treatment increased from 25% to 75% of the duration of tamoxifen treatment. For overall mortality, the risk increased from 13% to 46% as the proportion of combined treatment increased. The authors estimated that paroxetine use for 41% of tamoxifen treatment would result in 1 additional breast cancer death within 5 years of tamoxifen cessation for every 19.7 patients treated. Other SSRIs did not show significant associations between increasing treatment duration and mortality (BMJ 2010 Feb 8;340:c693).
For more information, see the Hormonal therapy for breast cancer topics in DynaMed.