Pathologists' perspective on the study design, analysis, and interpretation of proliferative lesions in lifetime and prenatal rodent carcinogenicity bioassays of aspartame

Pathologists' perspective on the study design, analysis, and interpretation of proliferative lesions in a lifetime rodent carcinogenicity bioassay of sucralose

Sucralose, a sugar substitute first approved for use in 1991, is a non-caloric sweetener regulated globally as a food additive. Based on numerous experimental animal studies (dating to the 1980s) and human epidemiology studies, international health agencies have determined that sucralose is safe when consumed as intended. A single lifetime rodent carcinogenicity bioassay conducted by the Ramazzini Institute (RI) reported that mice fed diets containing sucralose develop hematopoietic neoplasia, but controversy continues regarding the validity and relevance of these data for predicting health effects in humans. The present paper addresses the controversy by providing the perspective of experienced pathologists on sucralose-related animal toxicity and carcinogenicity data generally, and the RI carcinogenicity bioassay findings specifically, using results from publicly available papers and international regulatory authority decisions. In the authors' view, flaws in the design, methodology, data evaluation, and reporting of the RI carcinogenicity bioassay for sucralose diminish the value of the data as evidence that this agent represents a carcinogenic hazard to humans. This limitation will remain until the RI bioassay is repeated under Good Laboratory Practices and the design, data, and accuracy of the pathology diagnoses and interpretations are reviewed by qualified pathologists with experience in evaluating potential chemically-induced carcinogenic hazards.

Consideration of the variability in control tumor incidence data at the Ramazzini Institute in evaluating treatment-related effects following chemical exposure

The Ramazzini Institute (RI) has been conducting animal carcinogenicity studies for decades, many of which have been considered by authoritative bodies to determine potential carcinogenicity in humans. Unlike other laboratories, such as the U.S. National Toxicology Program (NTP), the RI does not provide a report or record of historical control data. Transparently documenting historical control data is critical in the interpretation of individual study results within the same laboratory. Historical control data allow an assessment of significant trends, either increasing or decreasing, resulting from changes in laboratory methods or genetic drift. In this investigation: (1) we compiled a dataset of the tumors reported in control groups of Sprague-Dawley rats and Swiss mice based on data included in published RI studies on specific substances, and (2) conducted case studies to compare data from this RI control dataset to the findings from multiple RI studies on sweeteners and corresponding breakdown products. We found considerable variability in the tumor incidence across multiple tumor types when comparing across control groups from RI studies. When compared to the tumor incidence in treated groups from multiple studies, the incidence of some tumors considered to be treatment-related fell within the variability of background incidence from the RI control dataset.