Environmental and heritable causes of cancer among 9.6 million individuals in the Swedish family‐cancer database

TLDR

Using the Swedish Family‑Cancer Database, tetrachoric correlations and structural equation modeling quantified genetic and shared environmental contributions to 15 common cancers. Genetic factors accounted for the largest proportion of risk in thyroid cancer (53%) and other sites, while shared environmental effects ranged up to 15% in stomach, indicating that environment is the main driver for most cancers except thyroid and that heritability explains only part of genetic risk.

Abstract

The genetic and environmental components in 15 common cancers were estimated using the nationwide Swedish Family-Cancer Database. Tetrachoric correlations were used to describe similarity in cancer liability among family members. Structural equation modeling was used to derive estimates of the importance of genetic and environmental effects. Statistically significant estimates of proportion of cancer susceptibility, accounted for by genetic effects, were obtained for all studied cancers except for leukemia. The estimate was highest in thyroid cancer (53%), followed by tumors at endocrine glands (28%), testis (25%), breast (25%), cervix (22%), melanoma (21%), colon (13%), nervous system (12%), rectum (12%), non-Hodgkin lymphoma (10%), lung (8%), kidney (8%), urinary bladder (7%), stomach (1%) and leukemia (1%). The estimates of shared environmental effects ranged from 0% (cervix) to 15% (stomach). The childhood shared environmental effects were most important in testicular cancer (17%), stomach cancer (13%) and cervix in situ (13%). Our results indicate that environment has a principal causative role in cancer at all studied sites except for thyroid. The relatively large effect of heritability in cancer at some sites, on the other hand, indicates that even though susceptibility genes have been described at many cancer sites, they are likely to explain only part of the genetic effects.