Objective: To determine the relative environmental and genetic influence in the development of carcinoma in situ (CIS) cervicis uteri.
Methods: Retrospective follow-up study with record linkage between The Danish Twin Register and The Danish Cancer Register. The study base comprises 27,004 female twins from 13,502 same-sex twin pairs. 5,258 were monozygotic and 8,244 dizygotic twin pairs. The statistic measurements are the coincidence ratio and the probandwise concordance rate in the two groups of twins with different zygosity.
Results: 750 twins were diagnosed with CIS cervicis uteri. 291 monozygotic twins came from 275 pairs and 459 dizygotic twins came from 435 pairs. There were 16 concordant monozygotic twin pairs and 24 concordant dizygotic pairs. The probandwise concordance rate was 0.11 (0.06-0.16) in monozygotic twins and 0.10 (0.06-0.14) in dizygotic twins.
Conclusion: A family clustering of CIS was demonstrated in both groups of zygosity. The probandwise concordance rate was equal in the monozygotic and the dizygotic groups, which means that genetic factors are not important in the development of the disease. However, a shared environment among twins plays a role in the development of CIS cervicis uteri.