Long-term follow-up of risk of cancer among twins

January 05, 2016

In a long-term follow-up study among approximately 200,000 Nordic twin individuals, there was an increased cancer risk in twins whose co-twin was diagnosed with cancer, with an increased risk for cancer overall and for specific types of cancer, including prostate, melanoma, breast, ovary, and uterus, according to a study in the January 5 issue of JAMA.

The global burden of cancer is considerable, with an estimated 12 million new cases and 8 million cancer deaths each year. In 2015 in the United States, 1.7 million individuals will be diagnosed with cancer and 590,000 will die of cancer, accounting for 1 in 4 deaths. Refinement of primary and secondary prevention strategies (i.e., factors that would have the greatest influence on reducing cancer incidence and death) requires a detailed understanding of the contribution of genetic and environmental factors to disease pathogenesis (the origination and development of a disease). Large twin studies of cancer can provide insight into the relative contribution of inherited factors and characterize familial cancer risk (risk of cancer in an individual given a twin's development of cancer) by leveraging the genetic relatedness of monozygotic (twins developed from the same fertilized egg [having the same genetic material]) and dizygotic (twins who develop from two separate fertilized eggs) twins, according to background information in the article.

Lorelei A. Mucci, Sc.D., M.P.H., of the Harvard T. H. Chan School of Public Health, Boston, and colleagues estimated familial risk and heritability (proportion of variance in cancer risk due to interindividual genetic differences) of cancer types among 80,309 monozygotic and 123,382 same-sex dizygotic twin individuals (n = 203,691) from the population-based registers of Denmark, Finland, Norway and Sweden. Twins were followed up a median of 32 years between 1943 and 2010. There were 50,990 individuals who died of any cause, and 3,804 who emigrated and were lost to follow-up.

A total of 27,156 incident cancers were diagnosed in 23,980 individuals, translating to a cumulative incidence of 32 percent. Cancer was diagnosed in both twins among 1,383 monozygotic (2,766 individuals) and 1,933 dizygotic (2,866 individuals) pairs. Of these, 38 percent of monozygotic and 26 percent of dizygotic pairs were diagnosed with the same cancer type. There was an excess cancer risk in twins whose co-twin was diagnosed with cancer, with estimated cumulative risks that were an absolute 5 percent higher in dizygotic (37 percent) and an absolute 14 percent higher in monozygotic twins (46 percent) whose twin also developed cancer compared with the cumulative risk in the overall cohort (32 percent).

For most cancer types, there were significant familial risks and the cumulative risks were higher in monozygotic than dizygotic twins. Heritability of cancer overall was 33 percent. Significant heritability was observed for the cancer types of skin melanoma (58 percent), prostate (57 percent), nonmelanoma skin (43 percent), ovary (39 percent), kidney (38 percent), breast (31 percent), and corpus uteri (a part of the uterus; 27 percent).

"The data provide strong evidence of an excess familial risk for 20 of the 23 cancer types, as shown by the comparison of familial risks for those cancers with the cumulative risk in the twin cohort overall," the authors write.

The researchers note that dizygotic pairs of twins are as genetically similar as siblings, so that familial risk estimates among dizygotic pairs are relevant for siblings who are born at separate times.

"This information about hereditary risks of cancers may be helpful in patient education and cancer risk counseling."
(doi:10.1001/jama.2015.17703; Available pre-embargo to the media at http://media.jamanetwork.com)

Editor's Note: Please see the article for additional information, including other authors, author contributions and affiliations, financial disclosures, funding and support, etc.

The JAMA Network Journals

Related Cancer Articles from Brightsurf:

New blood cancer treatment works by selectively interfering with cancer cell signalling
University of Alberta scientists have identified the mechanism of action behind a new type of precision cancer drug for blood cancers that is set for human trials, according to research published in Nature Communications.

UCI researchers uncover cancer cell vulnerabilities; may lead to better cancer therapies
A new University of California, Irvine-led study reveals a protein responsible for genetic changes resulting in a variety of cancers, may also be the key to more effective, targeted cancer therapy.

Breast cancer treatment costs highest among young women with metastic cancer
In a fight for their lives, young women, age 18-44, spend double the amount of older women to survive metastatic breast cancer, according to a large statewide study by the University of North Carolina at Chapel Hill.

Cancer mortality continues steady decline, driven by progress against lung cancer
The cancer death rate declined by 29% from 1991 to 2017, including a 2.2% drop from 2016 to 2017, the largest single-year drop in cancer mortality ever reported.

Stress in cervical cancer patients associated with higher risk of cancer-specific mortality
Psychological stress was associated with a higher risk of cancer-specific mortality in women diagnosed with cervical cancer.

Cancer-sniffing dogs 97% accurate in identifying lung cancer, according to study in JAOA
The next step will be to further fractionate the samples based on chemical and physical properties, presenting them back to the dogs until the specific biomarkers for each cancer are identified.

Moffitt Cancer Center researchers identify one way T cell function may fail in cancer
Moffitt Cancer Center researchers have discovered a mechanism by which one type of immune cell, CD8+ T cells, can become dysfunctional, impeding its ability to seek and kill cancer cells.

More cancer survivors, fewer cancer specialists point to challenge in meeting care needs
An aging population, a growing number of cancer survivors, and a projected shortage of cancer care providers will result in a challenge in delivering the care for cancer survivors in the United States if systemic changes are not made.

New cancer vaccine platform a potential tool for efficacious targeted cancer therapy
Researchers at the University of Helsinki have discovered a solution in the form of a cancer vaccine platform for improving the efficacy of oncolytic viruses used in cancer treatment.

American Cancer Society outlines blueprint for cancer control in the 21st century
The American Cancer Society is outlining its vision for cancer control in the decades ahead in a series of articles that forms the basis of a national cancer control plan.

Read More: Cancer News and Cancer Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.