A retrospective review at The University of Texas MD Anderson Cancer Center (MDACC) examining data from January 2020 to January 2024 evaluated self-reported, non-prescription fenbendazole use among cancer patients.
1. Prevalence & Annual Trends
Overall Frequency: Out of 297,223 total patients treated at MDACC during the four-year period, 182 patients (0.06%) self-reported taking fenbendazole as a non-prescription supplement. None of these patients received a prescription for fenbendazole from MDACC.
Steady Annual Reporting: Unlike ivermectin (which experienced a sharp surge in 2021 during the COVID-19 pandemic), reported fenbendazole use remained relatively stable year-over-year:
2020: 42 patients
2021: 47 patients
2022: 42 patients
2023–2024: 51 patients
2. Primary Cancer Types
General Demographics: Fenbendazole self-administration was most frequently reported by patients with metastatic disease, prostate cancer, and colorectal cancer (CRC).
Gastrointestinal (GI) Subgroup: Among patients with GI-related malignancies specifically, 42 patients took fenbendazole. The three most common GI diagnoses were colorectal cancer, pancreatic cancer, and metastatic disease to the liver and small intestine.
3. Dosing Unpredictability & Clinical Implications
High Dosing Variability: Patients reported 138 distinct dosages and administration frequencies for fenbendazole, underscoring the unstandardized nature of self-directed treatment.
Unclear Sourcing: The study noted that it was impossible to determine how patients acquired fenbendazole or how they established their chosen dosing regimens.
Inability to Assess Efficacy: Due to the wide variety of non-standardized schedules used outside a clinical trial setting, researchers could not draw conclusions regarding fenbendazole’s therapeutic efficacy or clinical safety.
Clinical Recommendation: The authors stressed that oncologists must maintain active awareness of outside, non-prescription supplements taken by their patients.
Nguyen, T. Q., Phan, U. T. T., Can, M. V., Nguyen, D. H., Han, B., & Hoang, B. X. (2025). Synergistic anti-tumor effect of fenbendazole and diisopropylamine dichloroacetate in immunodeficient BALB/c nude mice transplanted with A549 lung cancer cells. Translational Lung Cancer Research, 14(7), 2509–2521. https://doi.org/10.21037/tlcr-2024-1272
Olutayo, E., Phan, M. V., Willis, J., & Hu, Z. I. (2024). A single institutional experience on patterns of ivermectin and fenbendazole use among patients with gastrointestinal cancers [Abstract/Poster Session 818]. The University of Texas MD Anderson Cancer Center / Baylor University School of Nursing.
Park, D., Lee, J.-H., & Yoon, S.-P. (2022). Anti-cancer effects of fenbendazole on 5-fluorouracil-resistant colorectal cancer cells. Korean Journal of Physiology & Pharmacology, 26(5), 377–387. https://doi.org/10.4196/kjpp.2022.26.5.377
Vlachou, I., Parsonidis, P., Mamagkaki, A., Bouris, I., & Papasotiriou, I. (2022). Teaching an old dog new tricks: The case of Fenbendazole. Cancer Treatment and Research Communications, 32, Article 100601. https://doi.org/10.1016/j.ctarc.2022.100601
Wang, X., Tian, W., Wang, N., Yang, X., Liu, Z., Li, L., Zhao, T., Wang, C., Zhang, H., Yang, H., & Jia, Y. (2024). Transcriptome analysis reveals the anticancer effects of fenbendazole on ovarian cancer: An in vitro and in vivo study. BMC Cancer, 24(1), Article 1593. https://doi.org/10.1186/s12885-024-13361-9
