Question explored with the scientific record
For someone with metastatic prostate cancer who did successful triplet therapy and is now in the fifth year from a diagnosis of high volume and PSA almost 2000 and extensive bone mets and very good PSA and other blood work and recent scans everything is zero where we want it to be zero sometimes you read about ivermectin and fenbendazole. Would they be helpful in ensuring continued success at avoiding progression?
The short version: the evidence retrieved contains no clinical trial testing ivermectin or fenbendazole for preventing progression in metastatic prostate cancer after a deep response.
You are asking about two drugs that have never been studied for your exact situation. The evidence we have is all off-target. Ivermectin shows anti-cancer activity in petri dishes and mouse tumors through mechanisms like blocking AKT/mTOR and WNT signaling [13, 20], and a 2025 rat study found it shrank gliomas when delivered as a nanoparticle [14]. But those are different cancers, different doses, and different delivery systems. The same 2025 paper that reviewed ivermectin's antiviral claims showed its in vitro effects are driven by nonspecific membrane perturbation that overlaps with cell toxicity, and human plasma levels after standard doses never reach the concentrations needed for those effects [21]. Fenbendazole has exactly one human case report in cancer: an 80-year-old woman with lung cancer who took it and developed severe drug-induced liver injury with no antitumor response [26]. That is the entire human safety record for fenbendazole in oncology.
| Drug | Evidence type | Cancer tested | Outcome | Human dose relevant? |
|---|---|---|---|---|
| Ivermectin | In vitro + rat glioma | Breast, glioma, canine mammary | Growth inhibition at 5-12 µM | No – human Cmax ~0.3 µM [21] |
| Fenbendazole | One case report | Lung adenocarcinoma | Liver injury, no tumor change | Yes – 1 g/day caused hepatitis |
The mechanism you hope for is plausible in a dish but unproven in a human body, especially yours. You are five years out from a PSA of nearly 2000 with scans showing zero disease. That is a remarkable response to triplet therapy. Adding an unstudied drug with no human efficacy data and a documented risk of liver toxicity [26] is a gamble with no evidence it pays off. The burden of proof has not been met.
My call: do not add either drug. Your current regimen produced a deep remission. Protect your liver and kidneys, and let your oncology team monitor for the first sign of progression. Confidence: high that the evidence does not support using these drugs for your goal.
Sources used 26
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Ivermectin inhibits canine mammary tumor growth by regulating cell cycle progression and WNT signaling
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Membrane Perturbations and Assay Interferences by Ivermectin Explain Its In Vitro SARS-CoV-2 Antiviral Activities and Lack of Translatability
This Perspective demonstrates that ivermectin’s in vitro SARS-CoV-2 antiviral activity is driven by nonspecific membrane perturbation and assay interference, tightly correlates with host cell toxicity, and fails to translate clinically due to pharmacokinetic constraints and lack…
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Purinergic Receptor Nanoimmunoamplifiers Potentiate Chemoimmunotherapy Efficacy in Hepatocellular Carcinoma
A novel ivermectin–MnO2 nanoimmunoamplifier (IMN) was designed to potentiate chemoimmunotherapy for hepatocellular carcinoma by sustaining eATP signaling through P2X4R/P2X7R, alleviating tumor hypoxia, reducing eATP degradation via CD39/CD73, and robustly activating the NLRP3 in…
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Influence of increased doses of fenbendazole supramolecular complex on sheep’s organism
Twenty crossbred sheep were given fenbendazole supramolecular complex (FSMC) at therapeutic (2 mg/kg) and supra-therapeutic (6 and 10 mg/kg) doses; across clinical, hematological, and biochemical parameters, FSMC was well tolerated with no adverse effects detected.
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The behavioral teratogenic potential of fenbendazole: a medication for pinworm infestation
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Drug-Induced Liver Injury in a Patient with Nonsmall Cell Lung Cancer after the Self-Administration of Fenbendazole Based on Social Media Information
This case report describes an 80-year-old woman with advanced nonsmall cell lung cancer who developed severe drug-induced liver injury after self-administering fenbendazole based on social media information, with liver enzymes normalizing after cessation and no observed antitumo…
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