Recommendations for further revisions to improve the International Agency for Research on Cancer (IARC) Monograph program

In 2019, the International Agency for Research on Cancer (IARC) "Preamble to the IARC Monographs" expanded guidance regarding the scientific approaches that should be employed in its monographs. These amendments to the monograph development process are an improvement but still fall short in several areas. While the revised Preamble lays out broad methods and approaches to evaluate scientific evidence, there is a lack of specificity with regard to how IARC Working Groups will conduct consistent evaluations in a standardized, objective, and transparent manner; document systematic review and evidence integration actions, and substantiate how these actions and decisions inform the ultimate classifications. Furthermore, no guidance is provided to ensure Working Groups consistently incorporate mechanistic evidence in a robust manner using a defined approach in the context of 21st century knowledge of modes of action. Nor are the conclusions of the working groups subjected to outside, independent scientific peer review. Continued improvements and modernization of the procedures for evaluating, presenting, and communicating study quality, and in the methods used to conduct and peer-review evidence-based decision making will benefit the Working Group members, the IARC Monographs Programme overall, and the international regulatory community and public who rely upon the monographs. •In 2019, IARC issued the "Preamble to the IARC Monographs" with revised guidance on cancer hazard assessment.•The revisions lack specificity for Working Groups to assess agents in a standardized, objective, and transparent manner.•The revisions lack detail on analyzing modes of action and documenting systematic review and evidence integration actions.•Guidance is not provided for substantiating these decisions or how they should inform the ultimate cancer classifications.•We suggest improvements that will benefit Working Groups, regulatory communities, and the public.