FRIDAY, Feb. 6, 2009 (HealthDay News) -- Scientists have identified two gene mutations that appear to predict a significant increased risk of developing thyroid cancer.
This finding could lead to early diagnosis and treatment, the researchers said. In 2008, there were 37,340 new cases of thyroid cancer and 1,590 deaths, according to the U.S. National Cancer Institute.
"We found two single nucleotides polymorphisms that confer a risk of thyroid cancer," said lead researcher Dr. Kari Stefansson, CEO of deCODE Genetics, in Reykjavik, Iceland. "When you take the risk of both of them, they have almost six times the risk of thyroid cancer that the average person has," he said.
Stefansson noted the increased risk for thyroid cancer may be due to lower levels of a hormone perhaps regulated by these genes. These mutations are associated with lower levels of thyroid-stimulating hormone, he said.
"This is important in how the cancer develops," Stefansson said. "The thyroid-stimulating hormone is involved in differencing cells in the thyroid. If you have less stimulating hormone, you have less differencing of cells in the thyroid," he said. "We have put our finger on the mechanism whereby these mutations lead to the development of cancer."
The report was published in the Feb. 6 online edition of Nature Genetics.
Stefansson and his colleagues found two mutations that appear to increase the risk of thyroid cancer. These mutations, located on the 9q22 and 14q13 chromosomes, are the first gene variations identified that are associated with the risk of developing thyroid cancer, Stefansson noted.
To find these variations, Stefansson's group looked at the genome of 192 Icelanders with thyroid cancer and 37,196 people in the United States and Spain without the disease.
The researchers found that about 4 percent of people of European descent carry both mutations, increasing their risk 5.7 times for thyroid cancer compared with people without either mutation.
Combined, these mutations may account for about 57 percent of all cases of thyroid cancer. In addition, these variations may signal altered levels of a key hormone produced by the thyroid.
"This finding will lead to a wonderful diagnostic instrument that will allow us to develop a test to find people who are at an extraordinarily high risk of developing this disease," Stefansson said. "That is important, because if you diagnose thyroid cancers early, you have a very good chance of curing it," he said.
Stefansson said that people who have a family history would be the best candidates for this test.
Risk factors for thyroid cancer include smoking, as well as age and family history. Risk factors can influence the development of cancer, but most do not directly cause cancer. Some people with several risk factors never develop cancer, while others with no known risk factors do, according to the American Society of Clinical Oncology.
deCODE is a bio-pharmaceutical company developing drugs and DNA-based tests to improve treatment, diagnosis and prevention of common diseases.
Thyroid cancer expert Dr. Scott Rivkees, director of the Yale Pediatric Thyroid Center at Yale University, thinks this finding is an important contribution to the understanding of the disease, and a genetic test may be play a significant role in early detection of the condition.
"The report is a very important study and is the type of investigation that is needed for the field," Rivkees said. "Increasing evidence shows that there is a genetic component to thyroid malignancies."
This group has made a tremendous discovery in finding gene areas and genes that markedly increase the risk of thyroid cancer, Rivkees said. "Thyroid cancer is readily treated and has a wonderful long-term prognosis if detected early. The ability to identify individuals at increased risk for thyroid cancer through a genetic test may someday allow us to identify individuals who needed heightened screening for this form of cancer," he said.
However, Dr. Len Lichtenfeld, deputy chief medical officer of the American Cancer Society, doesn't think that these mutations could be used to predict the risk of thyroid cancer.
"They have demonstrated that there is a relationship between these genes and thyroid cancer," Lichtenfeld said. "But that relationship is not what I would call an absolute relationship, because these mutations were also in a significant percentage of the control patients as well."
One of the mutations was present in 35 percent of the population, and the other mutation was present in more than 50 percent of the population, Lichtenfeld noted. "Yes, these mutations occur with a higher frequency in patients with thyroid cancer compared to controls -- the reality is, they also appear in a fair number of control populations," he said.
These mutations are not discriminating enough to tell who is really at a higher risk of developing thyroid cancer, Lichtenfeld noted.
More information
For more on thyroid cancer, visit the American Cancer Society.
