fenbendazole cancer

The short version: the evidence for fenbendazole as a cancer treatment in humans is essentially absent, and the one human case report available shows liver injury with no tumor response.

The only human evidence in this retrieval is a 2021 case report of an 80-year-old woman with advanced lung cancer who took 1 gram of fenbendazole per day on a 3-days-on, 4-days-off schedule for about a month [2]. Her liver enzymes shot up sharply (AST from 24 to 386, ALT from 16 to 487) and the drug was rated a "probable" cause of the liver injury on the Naranjo scale [2]. Her tumors showed no change on CT scan, and her cancer progressed a few months later [2]. That is the entire human clinical record in this evidence set: one patient, no benefit, documented harm.

The rest of the evidence is either animal studies or veterinary parasite research. A 2024 mouse study tested fenbendazole combined with a CRISPR therapy for bladder cancer and found tumor shrinkage in mice, but that tells you almost nothing about whether it works in a human body at any safe dose [1]. The veterinary safety study in cats found no harm at very high doses, but cats are not humans, and the study was designed for a different species and a different purpose [5].

The mechanism that gets discussed online—fenbendazole disrupting microtubules in cancer cells, similar to some chemotherapy drugs—is biologically plausible. But plausible is not proven. No human trial has tested it. No safety data in cancer patients exists beyond that single case. And the dose people take from internet forums (often 1 gram per day) is the same dose that caused liver injury in the one documented case.

My call: there is no credible evidence that fenbendazole treats cancer in humans, and the only documented human use produced liver injury without benefit. Confidence: high.