Identical Twins Cancer Research Shows Higher Familial Risk of Developing any Cancer

A study published in The Journal of the American Medical Association reveals that there is a higher risk for one twin to develop cancer if the other twin has been previously diagnosed with one.

Over 200,000 twins from Denmark, Norway, Finland and Sweden were included in the study. Each of the twins was followed for a period of 32 years, from 1943 until 2010.

Lorelei Mucci is an associate professor at the Harvard T.H. Chan School of Health and the study's lead researcher. In a report by CBS News, Mucci says both fraternal and identical twins were included in the study to see how the disease affects different familial relationships.

Identical twins share the same genes while fraternal twins only share half. This is the same as ordinary siblings.

Compared to the general population, twins are not more likely to develop cancer. However, if an identical twin was diagnosed with cancer, there is a 14 percent chance that the other twin will also develop cancer.

In the case of fraternal twins, the likelihood of both twins developing cancer is only increased by 5 percent. The results of the study indicate that both a person's genes and the environment influence a twin's chances of developing cancer.

Mucci tells Live Science that a person's genes can elevate the risk of developing cancers by 30 to 60 percent. This includes cancers of the breast, testicles, uterus, kidneys, ovaries, prostate and skin.

Although there was an increased risk of for twins to develop the same type of cancer, this does not happen in all of the cases. The researchers believe that there is only a 33 percent chance of developing the same cancer.

Some of the subjects also developed cancers where genes played a minor part. These include cancers affecting the ovaries (39 percent), kidneys (38 percent), breast (31 percent), and uterine (27 percent) areas.

Dr. Stephanie Bernie is the head of the surgical oncology department at Lenox Hill Hospital in New York City. "If cancer was simply genetic, identical twins would be affected by cancer equally," Bernik told the news channel reporters.

In the same report Bernik added, "Although there was an increased risk of cancer amongst identical twins, there was not a 100 percent correlation, indicating that environmental factors also play a part in the development of cancers."

According to the science-based publication, the researchers believe that the results can help medical practitioners inform patients on the likelihood of developing a specific cancer, especially if a close family member has already been diagnosed with one.