The claim that “fenbendazole is a cure for cancer” is misleading. The source included in this claim is a podcast from breastcancer.org, where oncologist and medical advisor Brian Wojciechowski states that fenbendazole has typically been used to treat parasites in dogs. Scientists discovered that the drug prevents microtubules, which is part of the structural support that both normal and cancer cells need to survive. A study at Johns Hopkins revealed that fenbendazole stopped tumor growth in mice, as it affected the fast-growing cancer cells more than the healthy cells.
However, there have been no widespread tests on humans with cancer, or on how fenbendazole interacts with other medications someone with cancer may be taking. Dr. Wojciechowski emphasizes that he would definitely not recommend this drug to his patients due to lack of information about side effects. While fenbendazole has interesting medical potential and has proven effective in mice, defining it as a “cure for cancer” is a harmful and false statement.
The National Institute of Health supports this conclusion. The NIH article cited below confirms that fenbendazole does have "potential anticancer capabilities," but there must be extensive clinical trials before it can be safely and effectively prescribed to humans.
https://www.breastcancer.org/podcast/deworming-medicine
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9600184/