Fenbendazole belongs to a group of medicines called anthelmintics that are used to treat parasites, including worms

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some people with cancer might decide to take fenbendazole on their own without informing their cancer care team. People have self-reported becoming “cancer-free” after taking fenbendazole for breast, prostate, skin, and other cancers. But in most cases, the patients took fenbendazole at the same time as standard or traditional cancer treatments

https://www.cancer.org/cancer/latest-news/what-to-know-about-fenbendazole.html