Suicidality and Illness Course Worsening in a Male Patient withBipolar Disorder during Tamoxifen Treatment for ER+/HER2+Breast Cancer

Tamoxifen is a selective estrogenic receptor modulator (SERM) drug. In addition to its common use in breast cancer ER+,Tamoxifen has been object of growing interest in psychiatry as antimanic drug. At the same time, clinical concerns aboutTamoxifen’s depressogenic effect have been repeatedly raised even without reaching univocal conclusions. We discuss the caseof a 45-year-old-male with a diagnosis of Bipolar Disorder type II, treated with Tamoxifen as relapse prevention treatment aftersurgery for a ER+/HER2+ breast cancer. The patient required two psychiatric admissions in a few-month time span since heshowed a progressive worsening of both depressive and anxiety symptoms, with the onset of delusional ideas of hopelessnessand failure up to suicidal thoughts. The clinical picture showed poor response to treatment trials based on various associationsof mood-stabilising, antidepressants, and antipsychotic drugs. During the second hospitalization, after a multidisciplinaryevaluation, the oncologists agreed on Tamoxifen discontinuation upon the severity of the psychiatric condition. The patientunderwent a close oncological and psychiatric follow-up during the following 12 months.Methods. Psychiatric assessmentsincluded the Montgomery-Asberg Depression Rating Scale (MADRS), the Hamilton Depression Scale (HAM-D), the ColumbiaSuicide Severity Rating Scale (C-SSRS), and the Quality of Life Enjoyment and Satisfaction Questionnaire Short Form (Q-LES-Q-SF). All questionnaires were administered at the time of the second hospitalization and in a one-year follow-up.Results.Suicidal ideation fully remitted and depressive symptoms markedly and rapidly improved in the aftermath of Tamoxifendiscontinuation. The symptomatological improvement remained stable across one-year follow-up.Conclusions. Male patientswith a mood disorder history constitute a high-risk group as to Tamoxifen psychiatric side effects. The onset or worsening ofdepressive symptoms or suicidality should be carefully addressed and promptly treated, and clinicians should be encouraged toconsider the possibility of discontinue or reduce Tamoxifen therapy after a multidisciplinary evaluation