Abstract PS7-51: The impact of SSRI use on overall survival in breast cancer patients in northern Israel
Authors: Fischer Avital , Rennert Hedy , Barnett Ofra , Rennert Gad 
Published: February 2021

Abstract
Background: It is estimated that 12.7% of the US population had been prescribed an antidepressant in the past month and that women are twice as likely to be on an antidepressant than men. Therefore, it is especially important to understand how SSRIs interact with female hormones and influence risk and progression of female cancers, especially breast cancer, being the most common. Up to a third of women use selective serotonin reuptake inhibitors (SSRIs) after breast cancer diagnosis. Recent investigation has demonstrated serotonin receptor (5-HTR2B) expression in the breast and identified serotonin production in breast tumor cells as an indicator of poor prognosis. This paper presents a unique comparative assessment between the influence of prior SSRI use, continuous and after use relative to breast cancer diagnosis on overall mortality among breast cancer patients. This analysis is expected to provide a clearer understanding of the influence of SSRIs based on period of use relative to time of diagnosis on overall mortality. Methods: The present study includes a population-based sample of consecutively diagnosed breast cancer cases identified as part of the Breast Cancer in Northern Israel study. Patients were recruited and followed from January 1st, 2000 to July, 2019. Participants completed risk factor questionnaires regarding medical, reproductive, family and personal history of cancer, medication use and health habits. Additionally full prescription data was available through the Israeli national CLALIT medical database. An analysis of 5976 newly diagnosed women with breast cancer was performed. K-M survival analysis and time-dependent and time-independent COX proportional hazard models were performed to determine overall survival based on interval of SSRI use. Results: Use of SSRIs in the 5 years prior to breast cancer diagnosis was associated with a 66% increase in overall mortality (HRadj.=1.66; CI: 1.05-2.63). Use of SSRIs with use that initiated after breast cancer diagnosis was associated with an 81% increase in mortality (HRadj.=1.81; CI: 1.58-2.06). Use of SSRIs in the 5 years post-diagnosis was associated with a significant (P&lt;0.001) dose-response increase in long-term mortality (&gt;5 years). For 24 months of SSRI use after diagnosis, there was a 99% increase in mortality (HR=1.99; CI: 1.39-2.83). Conclusion: SSRIs used both prior to and after breast cancer diagnosis are associated with reduced overall survival in breast cancer patients. The effect of SSRIs on mortality persisted even after adjustment for tamoxifen and factors thought to mediate the relationship behind depression and increased mortality including increased age at diagnosis, comorbidities and stage at diagnosis pointing toward other mechanisms mediating the association between SSRIs and impaired survival in breast cancer patients. Additional research is needed to better understand who is susceptible to the adverse effects of SSRIs on breast cancer overall mortality. Treating depressive symptomatology is of high importance. The results presented here indicate that risks and benefits of SSRI use after breast cancer diagnosis should be weighed when initiating pharmachotherapy and additional research is needed to better understand why SSRIs are associated with worse outcomes in breast cancer patients.
Citation Format: Avital Fischer, Hedy Rennert, Ofra Barnett, Gad Rennert. The impact of SSRI use on overall survival in breast cancer patients in northern Israel [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS7-51.