Recent studies have reported substantial increases in cancer incidence in young adults under 40 years in the United States.
We applied hierarchical cluster analysis to identify cancer anatomical clustering, for 48 anatomic sites, using incidence trends since 1973 for 25- to 39-year-olds.
Temporal trends mapped to three major clusters in men involving six organ systems (digestive, endocrine, urinary, blood, respiratory, and male genital) and one cluster in women involving five systems (digestive, endocrine, urinary, female genital, central nervous system). For both men and women, kidney, thyroid, and colorectal cancers consistently clustered for all ages 25–39 and for each 5-year age subgroup. Further, several cancers linked to the endocrine and digestive systems (three in men and six in women) had highly consistent temporal incidence trends.
These findings suggest that there may be organ system connections for cancers of the endocrine and digestive systems; etiologic approaches focused on clusters of cancers rather than individual cancers may prove fruitful.