Interspecific scaling of toxicity data

Area of Science:

• Toxicology
• Pharmacology
• Biostatistics

Background:

• Conventional methods for interspecies dose scaling in cancer risk assessment include body weight (BW) scaling and surface area (BW^0.67) scaling.
• These methods are crucial for extrapolating findings from animal studies to human cancer risk.
• The existing approaches have limitations in accurately reflecting physiological differences.

Purpose of the Study:

• To reexamine the conventional body weight and surface area scaling approaches used in cancer risk assessment.
• To propose and validate a more precise body weight scaling factor for interspecies extrapolation.
• To enhance the accuracy of cancer risk assessments by refining dose scaling methodologies.

Main Methods:

• Reanalysis of the Freireich et al. (1966) dataset on maximum tolerated doses (MTD) of anticancer agents in multiple species.
• Augmentation of the analysis with the Schein et al. (1970) dataset for additional chemotherapy agents.
• Statistical evaluation to determine the most appropriate body weight scaling exponent.

Main Results:

• The reanalysis indicated that body weight to the power of 0.75 (BW^0.75) provided a more accurate scaling factor for the 27 direct-acting compounds studied.
• This finding challenges the conventional use of surface area scaling (BW^0.67) in certain cancer risk assessments.
• The proposed BW^0.75 scaling factor demonstrated improved consistency across species for MTD extrapolation.

Conclusions:

• The BW^0.75 scaling factor is proposed as a more precise and appropriate method for interspecies extrapolation of maximum tolerated doses in cancer risk assessment.
• This refined approach can lead to more accurate predictions of human cancer risk from animal studies.
• Further validation of the BW^0.75 scaling factor across a broader range of compounds and toxicological endpoints is warranted.