Priorities for evaluation of agents for carcinogenicity by the IARC monographs program is determined by a process that includes an open call for recommendations by the public followed by a meeting and systematic evaluation by an advisory committee of international experts.  The most recent priorities meeting in 2024 considered over 200 candidate agents.
Priority was assigned by considering whether there was evidence that there is currently human exposure and, if so, the extent to which available evidence on carcinogenicity from each stream (human exposure, cancer in humans, cancer in experimental animals, and mechanistic evidence in humans and experimental systems) could support a new or an updated evaluation. 

On this basis a wide-range of agents were rated as a high-priority for evaluation from across the types including: infectious agents, biotoxins, complex exposures, occupations, particles, metals, pharmaceuticals, physical agents and pesticides.  About half these agents had never been evaluated by the monographs program, and the rest are already classified but new evidence could change the classification or were group 1 carcinogens with evidence for new cancer sites.  A smaller number of agents were classified as medium priority for evaluation.  These could become high priority if new evidence becomes available during the next 5 years.

Part of the rationale for publishing these priorities is to encourage scientists studying these agents to prioritize research that could help strengthen the formal evaluation.   This could include advancing publication of new study results, conducting targeted mechanistic studies or carrying out additional bias analyses.  There is increased emphasis on systematic bias assessment in the monograph evaluations and we recently summarized the wide-array of methods now available in an IARC scientific report.    Publications of results from quantitative bias analyses will greatly facilitate the work of the monograph review committee when they have to consider whether “bias, chance or confounding could explain the results”. 

There are many high priorities for the IARC monographs program to evaluate.  Through this dialogue between IARC, the priorities advisory committee and researchers we can all help facilitate the translation of important research findings into public health action.