Journal Issues Expression of Concern on the 197-Patient Ivermectin + Mebendazole Study
Anticancer Research flagged the widely-shared Hulscher et al. study (84.4% clinical benefit) with a formal Expression of Concern: no control group, self-reported outcomes. The paper has not been retracted as of August 2026.
By Sanare Lab · August 1, 2026 · 4 min read
Shortly after the widely cited 197-patient observational study on ivermectin + mebendazole was published in Anticancer Research (June 2026), the journal issued a formal Expression of Concern. The study has not been retracted, and the 84.4% clinical benefit rate figure is still technically in the literature — but the journal flagged two fundamental methodological problems: no control group, and outcomes based on patient self-reports.
The June 2026 Hulscher et al. study in Anticancer Research — reporting that 84.4% of 122 evaluable patients who took compounded ivermectin + mebendazole capsules reported clinical benefit — spread rapidly through repurposed-drug communities before its methodological limitations were fully absorbed. Now the journal itself has added a formal flag.
An Expression of Concern (EoC) is not a retraction. It signals that the journal has identified serious methodological or ethical issues that it believes readers must weigh when interpreting the results — but has not yet determined whether the findings should be formally withdrawn.
Table of Contents
The Original Study
| Parameter | Detail |
|---|---|
| Authors | Hulscher et al. |
| Journal | Anticancer Research, June 2026 |
| PubMed | PMID 42203321 |
| Design | Prospective observational cohort |
| Patients enrolled | 197 |
| Completed 6-month follow-up | 122 |
| Intervention | Compounded capsules: 25 mg ivermectin + 250 mg mebendazole |
| Primary finding | 84.4% clinical benefit rate (CBR): stable disease, regression, or NED |
| Tumor regression or NED | 48.4% of completers |
| Disease progression | 15.6% |
| Concurrent conventional therapy | Majority of patients — not controlled for |
What the Expression of Concern Said
The EoC pointed to two structural problems that the journal determined materially affect interpretation of the results:
1. No control group. Without a matched group of patients who received conventional therapy alone, it is impossible to determine whether the reported improvements are attributable to ivermectin + mebendazole, to the concurrent chemotherapy/radiation/immunotherapy most patients were also receiving, or simply to natural disease fluctuation. The study itself acknowledged this limitation — the EoC made it a formal flag.
2. Self-reported outcomes. Clinical benefit was assessed based on patients' own reports, not verified imaging, biomarker measurements, or independent medical record review. Self-report bias in cancer trials is well documented: patients who invest in a treatment they believe in tend to assess themselves as "stable" in ambiguous situations.
The Core Methodological Problems
| Issue | Why It Matters |
|---|---|
| No control arm | Cannot distinguish drug effect from standard therapy or natural history |
| Self-reported outcomes | Susceptible to placebo effect, wishful thinking, and recall bias |
| 75 patients lost to follow-up (197 → 122) | Dropout may not be random; patients who progressed may have left the study |
| No imaging verification | "Tumor regression" was not independently confirmed by radiology |
| Heterogeneous cancer types | Mixed tumor types make aggregate CBR figures difficult to interpret |
Status: Not Retracted
As of August 2026, the Hulscher et al. paper has not been retracted. An Expression of Concern leaves the study in the literature with an attached flag. The journal is either waiting for author response, requesting additional data, or conducting a formal investigation before deciding whether to proceed with retraction. In the interim, any citation of "84.4% clinical benefit" should be accompanied by disclosure of the EoC.
The 2025 fenbendazole case series (three Stage IV patients) provides a useful parallel: it was formally retracted in January 2026 for undisclosed conflicts of interest, but not because the clinical events described were disputed. Methodology and transparency are the thresholds most frequently triggering these actions — not falsification of outcomes.
The Viral Spread Problem
According to a subsequent analysis in The Conversation, the Hulscher et al. paper was downloaded more than 85,000 times before its official publication date — spread through health influencers, podcasts, and supplement community channels as a "breakthrough study." By the time the EoC was issued, the 84.4% headline had already been cited uncritically thousands of times.
This pattern — data spreading faster than peer critique — is not unique to this study. It is the structural challenge facing any positive-signal finding in a field where patient communities are highly motivated and well-networked. The practical consequence is that corrections and caveats never fully catch the original claim.
How to Read This Evidence
The EoC does not mean ivermectin or mebendazole lack anticancer activity. It means this particular study cannot be used as reliable evidence that they have it. The mechanistic case remains — both drugs have plausible cancer-relevant pathways in preclinical work — but the human outcome data is still missing a properly controlled trial. The ongoing ICONIC trial (NCT07487805) and the Cedars-Sinai breast cancer study (NCT05318469) are the right way to generate that evidence.
Until a properly controlled trial exists, the Hulscher study is best described as hypothesis-generating — a signal worth investigating, not a result worth acting on clinically.
FAQ
What is an Expression of Concern?
A formal notice from a journal indicating serious methodological or ethical concerns about a published paper. The paper stays in the literature with the flag attached. It is not a retraction — the journal has not determined the findings are false, only that they must be interpreted with significant caution.
Was the study retracted?
No. As of August 2026, the Hulscher et al. study has not been retracted. An Expression of Concern is a preliminary flag, not a withdrawal.
Does this mean ivermectin + mebendazole don't work?
Not necessarily. The EoC means this particular study cannot reliably prove they work. The mechanistic rationale from preclinical research is still intact. A properly controlled randomized trial is what's needed to answer the question — and none has been completed yet.
What was the 84.4% clinical benefit figure based on?
Patient self-reports at 6 months, without a control arm or imaging verification. 75 of the original 197 patients did not complete the 6-month follow-up and are not included in the 84.4% figure — their outcomes are unknown.
Which ongoing trials will give better data?
ICONIC (NCT07487805) studies ivermectin + immune checkpoint inhibitors in solid tumors (results expected late 2027). NCT05318469 at Cedars-Sinai studies ivermectin + immunotherapy in metastatic triple-negative breast cancer (expected completion October 2026).
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References
- Hulscher JBF, et al. "Real-world Clinical Outcomes of Ivermectin and Mebendazole in Cancer Patients." Anticancer Research. 2026;46(6):3243. PMID: 42203321 [Expression of Concern issued]
- Sanare Lab coverage of the original study: Ivermectin + Mebendazole: 84.4% Clinical Benefit in 197-Patient Study
- The Conversation. "Ivermectin isn't a cancer miracle drug — but influencers claim otherwise." July 2026. theconversation.com
- ICONIC Trial NCT07487805. ClinicalTrials.gov. clinicaltrials.gov
- Cedars-Sinai ivermectin + immunotherapy trial NCT05318469. clinicaltrials.gov
Medical Disclaimer
This article is for educational and informational purposes only. It is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.
Sanare Lab
Science-based health education team reviewing published research on repurposed drugs, integrative oncology, and evidence-based protocols.