Abstract

Background: The global burden of advanced-stage cancers remains a significant challenge, particularly in low- and middle-income countries where access to effective therapies is limited. Repurposing existing drugs, such as the anti-parasitic ivermectin, fenbendazole, and mebendazole, has garnered attention due to anecdotal reports suggesting potential anti-cancer effects.

Objective: This article compiles and systematically presents anecdotal case reports and preliminary clinical data on the use of ivermectin and benzimidazoles (fenbendazole and mebendazole) in patients with stage 4 cancers, aiming to provide a foundation for further scientific investigation.

Methods: Case reports were collected from various online sources, including social media platforms (e.g., X/Twitter) and websites, detailing patient experiences with ivermectin and benzimidazoles, often in combination with conventional therapies. Cases are organized by cancer type, with a focus on stage 4 diagnoses, and include reported outcomes such as tumor shrinkage, biomarker reduction, and imaging results.

Results: A total of 140+ case reports across multiple cancer types (breast, brain, bile duct, bladder, cervical, colorectal, esophageal, endometrial, head and neck, kidney, liver, lung, ovarian, pancreatic, prostate, sarcoma, and skin) were compiled. Notable outcomes include significant tumor volume reductions (e.g., up to 99.7% in pancreatic cancer), biomarker decreases (e.g., CA19-9 dropping from 44,960 to 21 in pancreatic cancer), and reports of "cancer-free" status in some cases. A phase I/II clinical trial on ivermectin and balstilimab in metastatic triple-negative breast cancer reported a 37.5% clinical benefit rate.

Conclusion: These anecdotal reports suggest potential anti-cancer effects of ivermectin and benzimidazoles, warranting further investigation through rigorous clinical trials. Patients should consult oncology specialists to integrate these findings into personalized treatment plans, as the evidence remains preliminary.

Keywords: Ivermectin, fenbendazole, mebendazole, repurposed drugs, advanced cancer, case reports, integrative oncology.

Introduction

Access to effective, cancer-specific therapies remains limited, particularly in low- and middle-income countries where cancer survival rates lag those in high-income settings due to inadequate funding and infrastructure (1, 2). This has led to increased interest in repurposing existing drugs as more affordable alternatives. Exploring such options may provide valuable insights and potential solutions for expanding treatment accessibility, warranting further scientific investigation.

Traditional cancer therapies, including surgery, chemotherapy, radiation, targeted therapy, and immunotherapy, have low documented survival rates and outcomes for advanced, metastatic, and stage 4 cancers:

• Stage 4 Breast Cancer 5-year relative survival rate: 26% (distant/metastatic) (7).
• Stage 4 Colorectal Cancer 5-year survival rate: 13% (distant) (7).
• Lung Cancer (Stage III NSCLC): Addition of immunotherapy after chemo-radiation increased 3-year survival to 52% versus 44% for chemo-radiation alone in a large US study, published in JAMA. (8)

Ivermectin and benzimidazoles (fenbendazole and mebendazole), traditionally used as antiparasitic, have gained attention due to anecdotal reports of efficacy in cancer treatment, particularly for metastatic disease. Despite widespread discussion on social media platforms such as X, peer-reviewed clinical evidence remains scarce, limiting their integration into mainstream oncology. This article systematically compiles anecdotal case reports and preliminary clinical data on the use of ivermectin, fenbendazole, and mebendazole in stage 4 cancer patients.

The objective is to document these cases to stimulate hypothesis generation and encourage rigorous clinical research into these repurposed drugs as potential components of combination therapies.

Methods

Data Collection: Case reports were sourced from publicly available platforms, including X/Twitter, Substack, and other websites, as well as peer-reviewed literature where available. Reports were selected based on their documentation of ivermectin and/or benzimidazole use in stage 4 cancer patients, with outcomes such as tumor size reduction, biomarker changes, or imaging results.

Inclusion Criteria: Cases involved patients with stage 4 cancers treated with ivermectin, fenbendazole, or mebendazole, either alone or in combination with conventional therapies (e.g., chemotherapy, immunotherapy).

Data Organization: Cases are presented alphabetically by cancer type, with details on patient demographics, treatment protocols, and outcomes. Where applicable, quantitative data (e.g., tumor size, biomarker levels) are included to provide measurable outcomes.

Ethical Considerations: As this is a compilation of publicly shared anecdotes, no direct patient interaction or ethical approval was required. However, patient anonymity was preserved where possible.

Results

The compilation includes over 140 case reports across 17 types of cancer, with selected cases summarized below.

Discussion

The compiled case reports suggest potential anti-cancer effects of ivermectin and benzimidazoles, often in combination with conventional therapies. Reported mechanisms include inhibition of the WNT-TCF pathway [4], induction of apoptosis, and chemo sensitization/radio sensitization [5, 6]. Notable outcomes include significant tumor volume reductions (e.g., 99.7% in pancreatic cancer), biomarker decreases (e.g., PSA from 2093 to 39 in prostate cancer), and improved quality of life. However, these reports are anecdotal, lacking the rigor of controlled clinical trials, and are subject to biases such as self-selection and incomplete follow-up.

The phase I/II trial on ivermectin and balstilimab [3] provides preliminary clinical evidence, but larger, randomized controlled trials are needed to establish efficacy and safety. Differences in response rates (e.g., variable efficacy in prostate cancer) and optimal dosing (e.g., higher doses of ivermectin at 1-2 mg/kg/day vs. lower doses in some cases) highlight the need for standardized protocols. Additionally, the cost-effectiveness of fenbendazole (~$0.48 per 222 mg dose) compared to mebendazole (~$450 per pill in the US) underscores the potential for accessible therapies, particularly in resource-limited settings.

Limitations: The anecdotal nature of these reports limits their generalizability. Lack of control groups, variable treatment protocols, and potential confounding from concurrent therapies (e.g., chemotherapy, immunotherapy) complicate attribution of outcomes to ivermectin or benzimidazoles. Furthermore, social media sources are not indexed in scientific databases, increasing the risk of misinformation.

Conclusion

This compilation of anecdotal case reports provides preliminary evidence of the potential anti-cancer effects of ivermectin and benzimidazoles in stage 4 cancers. This comprehensive compilation of advanced cancer case reports and preliminary clinical trial data highlights a growing interest in repurposing anti-parasitic agents for oncology. While ivermectin and fenbendazole are not established universal cures, their safety profiles and observed anecdotal responses justify further clinical investigation (9, 10).

For example, case reports and small clinical studies with mebendazole have documented tumor regression or disease stability in individual patients with metastatic cancers, and phase I trials have shown that high dose mebendazole can be administered safely in combination with standard treatments (11). Fenbendazole has demonstrated anti-cancer effects in laboratory studies and some animal models. Ivermectin has shown anti-tumor effects in preclinical studies and is being evaluated in early-phase clinical trials.

With their low cost and accessibility, ivermectin and benzimidazoles represent promising candidates for further investigation—either as standalone treatments or in combination with traditional therapies—for patients with advanced cancers. This work seeks to encourage additional research into repurposed drugs as part of a comprehensive multimodal approach to cancer care.

Acknowledgments

The authors acknowledge the contributions of patients and advocates who shared their experiences on public platforms, as well as researchers like Dr. William Makis for their efforts in documenting these cases.

Disclosures

The authors declare no conflicts of interest. This work is for informational and research purposes only and does not constitute medical advice. Patients should consult healthcare providers before initiating any treatment.