Mebendazole, a prescription drug used in humans to treat parasites, and fenbendazole, a treatment for parasites in animals, show promising but so far very preliminary evidence of anticancer effects.

How can mebendazole or fenbendazole help you? What the research says

We summarize the clinical evidence for each medical benefit here. We begin with our assessment of the strength of evidence within each category, followed by a brief summary of individual studies or reviews of several studies. In assessing the strength of evidence, we consider the study design, number of participants, and the size of the treatment effect (how much outcomes changed with treatment).

To see more details, click the plus sign to the right of any section.

Improving treatment outcomes

Is mebendazole or fenbendazole linked to improved survival? Is it linked to less cancer growth or metastasis? Does it enhance the anticancer action of other treatments or therapies? We present the evidence.

Advanced cancer

People with metastatic colorectal cancer have shown tumor responses including slower disease progression after treatment with chemotherapy when also treated with mebendazole. Mebendazole may show similar effects in metastatic adrenal cancer, but no benefit has been found among people with unresponsive (refractory) gastrointestinal cancer.

Brain cancer

Adding mebendazole to treatment with either lomustine or temozolomide for people with recurrent glioblastoma did not lead to a meaningful clinical benefit.

Mebendazole combined with other therapies

Combining mebendazole with other therapies may show some benefits on survival and/or cancer progression:

  • Mebendazole and temozolomide with high-grade gliomas
  • Simvastatin, metformin, niclosamide, mebendazole, itraconazole, loratadine, and chloroquine with recurrent platinum-resistant clear-cell ovarian cancer

Preclinical evidence

Beyond the clinical (human) evidence presented above, preclinical evidencetesting a drug, a procedure, or another medical treatment in isolated cells or in animals; preclinical evidence is considered only an initial indication of possible effects in people (cell and animal studies) shows anticancer responses and/or longer survival in these cancer types:

  • Adrenocortical carcinoma
  • Advanced cancer
  • Brain and nervous system cancer
  • Breast cancer, including triple-negative breast cancer
  • Colorectal cancer
  • Gallbladder cancer (cholangiocarcinoma)
  • Head and neck squamous cell carcinoma 
  • Intestinal cancer
  • Leukemia
  • Liver cancer
  • Lung cancer
  • Melanoma
  • Oral squamous carcinoma
  • Ovarian cancer
  • Pancreatic cancer
  • Peritoneal cancer
  • Stomach (gastric) cancer
  • Thyroid cancer

Preclinical evidence is summarized in Are you a health professional? ›

Optimizing your body terrain

Does mebendazole or fenbendazole promote an environment within your body that is less supportive of cancer development, growth, or spread? We present the evidence.

See Optimizing Your Body Terrain ›

Find medical professionals who specialize in managing body terrain factors: Finding Integrative Oncologists and Other Practitioners ›

Your microbiome

Children treated with mebendazole for parasites showed higher percentages of probioticliving microorganisms (bacteria and some yeasts) that, when consumed in sufficient numbers, can provide health benefits that go beyond basic nutrition; benefits may include supporting gut and immune health and contributing to the maintenance of a balanced gut microbiota. Examples of probiotic foods are yogurt, kefir, sauerkraut, tempeh and kimchi and anti-inflammatory microbes. We don’t know if people with cancer would find a similar benefit.

Preclinical evidence 

Preclinical evidencetesting a drug, a procedure, or another medical treatment in isolated cells or in animals; preclinical evidence is considered only an initial indication of possible effects in people (cell and animal studies) shows mebendazole and fenbendazole each lower inflammation and oxidative stressan imbalance between free radicals and antioxidants in your body in which antioxidant levels are lower than normal; this imbalance can cause harmful oxidation reactions in your body chemistry. Preclinical evidence is summarized in Are you a health professional? ›

Reducing cancer risk

Is mebendazole or fenbendazole linked to lower risks of developing cancer or of recurrence? We present the evidence.

Preclinical evidence

Preclinical evidence (cell and animal studies) shows mebendazole delays the formation of these malignancies:

  • Fewer malignant peripheral nerve sheath tumors related to neurofibromatosis 1
  • Lower markers of colorectal cancer with familial adenomatous polyposis (FAP)
  • Lower incidence of pancreatic cancer

Preclinical evidence is summarized in Are you a health professional? ›

Also see evidence that fenbendazole may behave as a tumor promoter when given after specific tumor initiators in Safety and precautions ›

Keep reading about mebendazole or fenbendazole


Nancy Hepp, MS

Lead Researcher
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Ms. Hepp is a researcher and communicator who has been writing and editing educational content on varied health topics for more than 20 years. She serves as lead researcher and writer for CancerChoices and also served as the first program manager. Her graduate work in research and cognitive psychology, her master’s degree in instructional design, and her certificate in web design have all guided her in writing and presenting information for a wide variety of audiences and uses. Nancy’s service as faculty development coordinator in the Department of Family Medicine at Wright State University also provided experience in medical research, plus insights into medical education and medical care from the professional’s perspective.

Nancy Hepp, MS Lead Researcher


Andrew Jackson, ND

Research Associate
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Andrew Jackson, ND, serves as a CancerChoices research associate. As a naturopathic physician practicing in Kirkland, Washington, he teaches critical evaluation of the medical literture at Bastyr University in Kenmore, Washington. His great appreciation of scientific inquiry and the scientific process has led him to view research with a critical eye.

Andrew Jackson, ND Research Associate

Last update: May 21, 2024

Last full literature review: February 2024

CancerChoices provides information about integrative in cancer care, a patient-centered approach combining the best of conventional care, self care and evidence-informed complementary care in an integrated plan cancer care. We review complementaryin cancer care, complementary care involves the use of therapies intended to enhance or add to standard conventional treatments; examples include supplements, mind-body approaches such as yoga or psychosocial therapy, and acupuncture therapies and self-care lifestyle actions and behaviors that may impact cancer outcomes; examples include eating health-promoting foods, limiting alcohol, increasing physical activity, and managing stress practices to help patients and professionals explore and integrate the best combination of conventionalthe cancer care offered by conventionally trained physicians and most hospitals; examples are chemotherapy, surgery, and radiotherapy and complementary therapies and practices for each person.

Our staff have no financial conflicts of interest to declare. We receive no funds from any manufacturers or retailers gaining financial profit by promoting or discouraging therapies mentioned on this site.

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