A single institutional experience on patterns of ivermectin and fenbendazole use among patients with gastrointestinal cancers.

818 Background: The use of ivermectin and fenbendazole as supplemental therapy for cancer treatments have become increasingly visible and promoted in Western social media. There is a lack of information on patterns of ivermectin and fenbendazole use among patients with cancer. We sought to determine the patterns of ivermectin and fenbendazole use among patients with gastrointestinal (GI) malignancies at a single cancer institution in the United States. Methods: Using SAP BusinessObjects Web Intelligence (SAP Webi), a secure, web-based application with controlled institutional access, we conducted a retrospective review of all patients that visited MD Anderson Cancer Center (MDACC) from January 2020 to January 2024 who self-reported taking ivermectin and fenbendazole as non-prescription medications. Results: We identified 499 patients taking ivermectin and 182 patients taking fenbendazole as supplemental therapy at MDACC. These patients did not receive a prescription from MDACC for fenbendazole or ivermectin. Of all patients that visited MDACC from 2020 to 2024, 0.17% (499/297223) and 0.06% (182/297223) took ivermectin and fenbendazole, respectively. Ivermectin use annually among patients were 19, 241, 143, and 96 from 2020 to 2024. Fenbendazole use annually among patients were 42, 47, 42, and 51 from 2020 to 2024. There were 154 and 138 different dosages and frequencies of ivermectin and fenbendazole reported by patients, respectively. Patients with metastatic disease, prostate, and colorectal cancers (CRC) most frequently took fenbendazole. Patients with metastatic disease, breast, and prostate cancers most frequently took ivermectin. Among patients with GI-related malignancies, 85 patients and 42 patients took ivermectin and fenbendazole, respectively. The three most common disease types among GI malignancies were CRC, pancreatic, and metastatic disease to the liver and small intestine. Conclusions: The overall frequency of self-reported ivermectin and fenbendazole use among patients with GI cancers treated at MDACC were relatively small. There was notably an increase in ivermectin use in 2021, which may be attributed to the ongoing COVID-19 pandemic at the time. Although ivermectin use decreased after the development of new COVID-19 treatments, it did not go down to pre-pandemic levels. It appears to have been organically adopted as a supplement for cancer treatments after 2021. Given the wide range of dosages and frequencies used in a nonclinical trial setting, we are not able to draw any conclusions on the efficacy of ivermectin and fenbendazole in GI cancers. We also were not able to determine where patients were obtaining ivermectin and fenbendazole and how patients determined frequency and dosing of the drugs. Physicians should be aware of the patterns of outside supplements in cancer patients.