Microtubules are critical to cell function by providing the necessary structures for the cell to function. As a benzimidazole, Fenbendazole inhibits microtubule polymerization. This means that Fenbendazole can help starve out certain cancers by limiting their spread and growth, potentially allowing the patient to overcome them.
Of course, that is a gross oversimplification. Many studies are being performed on Fenbendazole, and it is too early to state the efficacy of the medication. However, it is also important to state that there have been cases of usage on both animals and people, resulting in a reduction or remission of many cancer types.
For more information on Fenbendazole, dosing, and other information, we have written a post prior that offers a reasonably extensive overview on the topic matter.