Effects of Tamoxifen as an Antifungal Agent against Oral Cavity Yeasts In-Vitro and in Breast Cancer Patients

Background: Tamoxifen (TAM) is an effective agent for the treatment of breast cancer and has antifungal activity against various fungi. However, the antifungal effects of TAM in-vivo and in patients under treatment remain unclear. Objectives: The present study aimed to investigate the antifungal effects of TAM on yeast oral flora in-vitro and in breast cancer patients. Methods: In this case-control study, the antifungal effects of TAM were assessed on 50 breast cancer patients receiving TAM treat- ment, 50 breast cancer patients without TAM treatment, and 50 healthy controls. The disc-diffusion method was used to determine the antifungal effects of TAM on six clinical yeast isolates in-vitro. Results: The number and species count of the yeasts were extremely low in the patients undergoing TAM treatment compared to the other subjects. On the other hand, the absence of the isolates was more evident in the patients receiving TAM treatment (96%). Candida albicans was frequently isolated from all the subjects. In the in-vitro tests, all the yeasts were susceptible to the two concentrations of TAM (5 and 10 μg/mL) at varying degrees. In addition, C. intermedia was the most susceptible yeast species to TAM with a low minimal inhibitory concentration (3.8 μg/mL). Conclusions: According to the results, TAM exerted significant antifungal effects on the yeasts of the oral cavity in the breast cancer patients, showing superior inhibitory effects compared to clotrimazole. Therefore, TAM is recommended as a promising antifungal, while further investigation is required regarding its safety.