Familial Risk and Heritability of Cancer Among Twins in Nordic Countries
- Study type
- Observational study
- Study name
- NorTwinCan
- Design
- Population-based prospective cohort study (twin registries of Denmark, Finland, Norway and Sweden)
- Sample size
- 203,691 twin individuals (80,309 individuals from monozygotic twin pairs and 123,382 individuals from same-sex dizygotic twin pairs)
- Source
- JAMA · 2016
In plain words
In this large study, cancer was tracked in more than 200 thousand twins in four Nordic countries for about 32 years. The results showed that if one twin gets cancer, the other twin's risk of cancer is higher, and this increase is greater in identical twins than in non-identical twins. About 33% of the differences in cancer risk between people were due to genetic factors. The genetic contribution was significant for cancers such as melanoma, prostate, ovarian, kidney and breast cancer, but this does not mean that getting cancer is certain.
Key results
Treatment arms and regimens
80,309 individuals. The study was observational and no treatment was given; the exposure was shared environmental factors and inherited risk factors within twin pairs.
123,382 individuals. The study was observational and no treatment was given; the exposure was shared environmental factors and inherited risk factors within twin pairs.
Source of the regimen details: Abstract of the paper
Doses are given for the information of specialists, as in this study’s protocol, and are not a prescription. Every drug must be prescribed by the treating physician for the individual patient.
Study population
Monozygotic and same-sex dizygotic twin individuals recorded in the population-based registries of Denmark, Finland, Norway and Sweden. Twins were followed for a median of 32 years between 1943 and 2010. 50,990 individuals died of any cause and 3804 emigrated and were lost to follow-up.
Endpoints
The main outcome was cancer incidence. Time-to-event analyses were used to estimate "familial risk" (the risk of cancer in an individual given a twin's cancer diagnosis) and "heritability" (the proportion of variance in cancer risk due to genetic differences between individuals). Follow-up was through cancer registries. Statistical models were adjusted for age and follow-up time and accounted for censoring and the competing risk of death.
Safety and side effects
The study was observational with no intervention, so treatment adverse events were not reported.
Clinical significance and place in guidelines
This study provides population estimates of familial risk and heritability for different cancers, which can be used in patient education and cancer risk counselling. It is observational and makes no specific treatment or screening recommendation; its status in clinical guidelines should be checked separately.
Limitations
This summary is based only on the abstract, which does not state the study's limitations; this section should be reviewed against the full text of the paper. Heritability is a population estimate and not a definite prediction for an individual. An erratum for this paper was published in JAMA on 23 February 2016 and should be checked.
This summary was prepared by the editorial team from the published paper; the original paper is the final reference. Read the original abstract on PubMed.