A new study based on a large review of twins has shown that environment and genetics have shared roles in determining the risk of cancer.
According to a report published online on the website Webmed, the risk of cancer increases for a person having an identical twin diagnosed with cancer. The risk associated with this hereditary factor increases the other twin's risk of any form of cancer, according to lead researcher Lorelei Mucci from the Harvard T.H. Chan School of Public Health in Boston.
The large review was based on studying a group of over 200,000 twins, both fraternal and identical, according to Medical News Today. The population of twins was chosen from countries such as Sweden, Norway, Finland and Denmark. This group of twins was followed around 32 years, in the period dating from 1943 to 2010, and they are part of the Nordic Twin Study of Cancer.
Professor Mucci explained that the conclusion of the study means that some families, based on their gens, carry a shared increased risk for any type of cancer. She added that this is a new area that medical community is "just learning about". However, according to the lead researcher, depending on the type of cancer, the influence of genetics varies in a wide range.
For instance, skin, testicular and prostate cancers were proved to be influenced strongly by genetics, while rectal, colon and lung cancers were found to be influenced largely by environmental factors.
Professor Mucci also explained the reasons why the study compared fraternal twins with identical twins. This is because fraternal twins are just like ordinary siblings, while identical twins share 100 percent of their genes.
During the study, around one-third of the participants have developed cancer. Overall, the study has found that twins are not more likely to develop cancer than the general population. However, a twin carry a 14 percent increased risk of cancer in case that one identical twin developed any cancer, according to researchers.
