Looking for genes that could boost a person's risk of cancer is not likely to reap great rewards, according to new research. While vast sums of money and resources are being invested in the search for common, inherited genetic variants that increase susceptibility to cancer, scientists now say that such genes probably don't exist. And if they do, they probably won't have much effect on the incidence of cancer, according to Dr. Stuart Baker, from the US National Cancer Institute, and Dr. Jaakko Kaprio, from the University of Helsinki, Finland.
Studying The Studies
The experts point to studies suggesting that the environment, diet and lifestyle have a much larger effect on the incidence of cancer than genetics. Those studies have found changes in cancer rates within one or two generations, which is just too quick to be related to the introduction of new genes, Baker and Kaprio note.
The idea that your genetic makeup is going to be the main factor that determines your susceptibility to cancer has been oversold, explains Dr. Michael Thun, vice president of epidemiology and surveillance research at the American Cancer Society. "The things we know that are bad for you are bad for you in so many different ways that they won't become OK just because you're less susceptible to one or another disease," he says. Most of the genetic changes that cause cancer happen during your lifetime, not at birth, he adds.
A pivotal study of cancer in twins also suggests that genes are not the key culprits in this disease. Looking at the data from identical and non-identical twins, that study found that genetic susceptibility had only a small-to-moderate effect on the incidence of cancer.
Baker and Kaprio both believe that studies that have shown a strong association between specific genes and a higher risk for cancer may be biased.
However, they note that certain genes may increase the risk for very specific types of cancer-for example, the BRCA1 and BRCA2 genes, which doctors know are strongly linked to breast cancer. But genes that encourage cancer in general are less likely, they say.
Still, "research on what the genetic changes are that give rise to a cancer is already profoundly important," Thun says. "The age of the human genome is here. The understanding of genes will transform the way we think about many diseases, and is already transforming the way we understand cancers."
