Expression of Concern.

Regarding: Hulscher et al., “Real-world Clinical Outcomes of Ivermectin and Mebendazole in Cancer Patients: Results from a Prospective Observational Cohort,” Anticancer Research Vol. 46, No. 6, pp. 3243-3255, 2026. The Editorial Board of Anticancer Research is issuing an official Expression of Concern regarding the article cited above. The study was published purely as “hypothesis-generating", opening the discussion for repurposing of these substances, establishing the ground for future approved, randomized clinical trials. Following publication, serious scientific concerns were raised by the international medical community regarding the verifiability and statistical reliability, and ethical oversight of the underlying dataset. In formal correspondence to the journal dated June 4, 2026, the authors clarified that the study cohort was not drawn from an unverified consumer survey, but instead comprised “provider-screened cancer patients enrolled in a structured prospective cohort” managed via an internal clinical workflow and licensed provider consultations. While the Editorial Board acknowledges the authors' transparency regarding the text-level limitations of selfreported data, a study published in a peer-reviewed oncology journal that reports a “Clinical Benefit Ratio of 84.4%” and specific percentages of “tumor regression” must rest on a verifiably real clinical foundation and adhere to established ethical frameworks for human subject research to maintain its validity in the permanent scholarly record. Anticancer Research does not endorse or condone the unvalidated off-label use of medications for unapproved oncological indications. Disclosing limitations does not exempt a clinical dataset from the foundational scientific requirements of empirical verifiability and independent ethical oversight. Accordingly, based on the authors' confirmation of an established clinical provider-patient workflow, the journal is initiating a formal Post-Publication Data Integrity and Ethical Oversight Audit. This investigation will evaluate the mandatory Institutional Review Board (IRB) approval or exemption documentation, the de-identified, source-verified clinical records confirming the baseline cancer diagnoses of the 197 initial participants and the objective medical documentation supporting the reported anatomical regressions. This Expression of Concern will remain prominently appended to the publication record online and in all indexing databases while this formal data and ethical verification audit is underway.