The Nordic Twin Study of Cancer

The Nordic Twin Study of Cancer (NorTwinCan), launched in 2008 and funded largely by the Ellison Foundation, is the largest twin study in the world available for the research of the heritability and familial risk of cancers such as prostate, breast, ovarian, and colon cancer.

Project leaders

Principal Investigator at Harvard School of Public Health: Lorelei Mucci

Principal Investigator at MEB:

Professor emeritus

Hans-Olov Adami

Phone: +46-(0)8-524 861 80


Kamila Czene

Phone: +46-(0)8-524 861 44
Organizational unit: Department of Medical Epidemiology and Biostatistics (MEB), C8

Project description

This one-of-a-kind database is comprised of nationwide Nordic Twin Registries from Denmark, Sweden, Finland, and Norway and, remarkably, includes over 300,000 twins with data linked on cancer incidence and mortality over and average of five decades of follow-up. Equally important is the comprehensive, multi-disciplinary team that disentangles the relative importance of environment versus genetic factors and related information relative to specific cancers. This group is comprised of prominent researchers and biostatisticians from National Twin Registries and academic institutions in the four Nordic countries that are involved, as well as from Harvard School of Public Health. In 2000, Paul Lichtenstein published “Environment and Heritable Factors in the Causation of Cancer – Analyses of Cohorts of Twins from Sweden, Denmark, and Finland,” in the New England Journal of Medicine, which has been cited in peer-reviewed literature more than 1200 times.  Among other goals, this collaboration seeks to expand on that paper with an added registry (Norway) and a decade more of follow-up. This added data allows the researchers to analyze rare cancers, and when paired with the newly developed statistical methods, it gives more power and strength to the estimations of heritability. In addition, the NorTwinCan team is poised to delve deeper into more specific areas such as lung cancer, colon/rectal cancer, breast cancer, prostate cancer, and cancer resistance. 

Because the first wave of analyses - including all cancers as well as the quantitatively dominating sites - the team NorTwinCan investigators is currently discussing the next phase which will include new analyses following extended follow-up.


Country Name
Sweden Hans-Olov Adami
USA Lorelei Mucci, Peter Kraft, Kathryn Penney.
Denmark Jacob Hjelmborg, Niels Holm, Axel Skytthe, Thomas Scheike.
Finland Eero Pukkala, Jaakko Kaprio, Tellervo Korhonen, Alfredo Ortega-Alonso.
Norway Jennifer Harris, Ingunn Brandt, Thomas Sevenius-Nilsen.


The heritability of prostate cancer in the Nordic Twin Study of Cancer.
Hjelmborg J, Scheike T, Holst K, Skytthe A, Penney K, Graff R, et al
Cancer Epidemiol. Biomarkers Prev. 2014 Nov;23(11):2303-10

The Heritability of Breast Cancer among Women in the Nordic Twin Study of Cancer.
Möller S, Mucci L, Harris J, Scheike T, Holst K, Halekoh U, et al
Cancer Epidemiol. Biomarkers Prev. 2016 Jan;25(1):145-50

Familial Risk and Heritability of Cancer Among Twins in Nordic Countries.
Mucci L, Hjelmborg J, Harris J, Czene K, Havelick D, Scheike T, et al
JAMA 2016 Jan;315(1):68-76

Read more about the twin study in the American press release.