Abstract P5-06-07: Desloratadine and loratadine increase breast cancer survival

Background: As tumors maintain an inflammatory microenvironment, anti-inflammatory medication can be used in cancer therapy. While H2-antihistamines have already shown effects as adjuvant anti-cancer drugs, H1-antihistamines have not been widely studied in this role, though they are among the most ubiquitously used medications globally, and have become increasingly sophisticated, affordable, and safe. Here, we aim to determine the effects of H1-antihistamines on breast cancer mortality. Methods: We investigated the effects of six H1-antihistamines (cetirizine, clemastine, desloratadine, ebastine, fexofenadine and loratadine) on breast cancer-specific and overall mortality in a nation-wide register-based study of all 61,627 Swedish women with newly diagnosed breast cancer July 1st 2005 - December 31st 2013. 14,711 women used H1-antihistamines. Both peri- and post-diagnostic antihistamine use was analyzed, using Cox regression models, and use in patient subgroups based on age or estrogen receptor status. Results: We found a consistently beneficial effect of desloratadine use (HR = 0·67; 95% CI 0·55-0·81, P Conclusions: We suggest immediate trials of desloratadine and loratadine as adjuvant treatment of breast cancer. Especially promising is the results for ER-breast cancer. Further studies on the effects of ebastine and possibly fexofenadine may be merited, as well as further studies of H1-antihistamines, particularly desloratadine, as treatment options for other malignancies. Citation Format: Hakan Lars Olsson, Ildiko Fritz, Philippe Wagner. Desloratadine and loratadine increase breast cancer survival [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P5-06-07.