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Study Finds Familial Link in Many Cancers

Children of victims likelier to have same tumor

MONDAY, Feb. 16, 2004 (HealthDayNews) -- A new study finds children of cancer sufferers may face a higher risk for inheriting the same type of cancer their parents had -- no matter which type of cancer it was.

German and Swedish researchers, looking into cancer incidences among family members, found the average risk that the children would inherit the same cancer as their parent was 5.5 percent. That contrasted with an average 3 percent risk found in the general population.

"This applies to all the cancers that we studied. The only connection that we didn't see that was significantly higher were those with a rare form of some cancers of connective tissue," says Dr. Kari Hemminki of the German Cancer Research Center in Heidelberg, Germany. "But generally we saw this link in all the cases."

Even stronger links were seen in several types of cancer. Males, for instance, had a 15 percent chance of getting prostate cancer. All persons whose parents had intestinal cancer had a 10 percent risk, while women had an 8.5 percent risk of breast cancer if their mother had it.

Some of the highest genetic risks were found in families with testicular cancer; the sons of affected fathers had four times the risk compared to sons of families without testicular cancer. Moreover, brothers of affected individuals had a nine times higher risk to develop this cancer.

Scientists had previously thought that only certain types of cancer carried a familial link. Hemminki's research, which looked through the Swedish family register, a record of all individuals born in Sweden after 1932 and comprising more than 10 million individuals, showed a link across almost all types of cancer.

Hemminki identified almost 5,000 families in which several cases of the same type of tumor occurred -- an indicator of familial cancer.

Based on the data, Hemminki calculated the familial risks for each tumor type with a high degree of accuracy.

Some caution, though, that environment might also play a role.

"The relative risks and types of cancers vary by study. It is assumed that the correlation is a function of shared genetic, environmental and lifestyle risks," says Dr. Mary B. Daly of the Fox Chase Cancer Center in Philadelphia. "As a result, the exact numbers seen in Sweden may be different from those seen in other ethnic groups."

Those in families with a known hereditary risk, such as those carrying BRCA1 or BRCA2 genes associated with breast cancer, should visit a cancer risk program, Daly adds.

"It is important to note that although the cancer risks are increased in children and siblings of cancer patients, typically two to fourfold, the absolute risk is still quite small for most cancers," says Douglas F. Easton, of Cancer Research UK. "Generally, therefore, no specific action is advised for individuals with just one affected relative." Those with a stronger family history may be referred to a cancer genetics clinic, he says.

But one need not worry as much if a relative outside the immediate family is affected, say a grandparent, uncle or cousin.

"You only inherit 50 percent of the genes from your genetic relation, so they are diluted quite fast," Hemminki says.

The report appeared in a recent issue of the International Journal of Cancer.

More information

Learn more about cancer and genetics from the American Cancer Society or the National Cancer Institute.

SOURCES: Kari Hemminki, M.D., Ph.D., Department of Biosciences at Novum, Karolinska Institute, Sweden, and German Cancer Research Center, Heidelberg, Germany; Mary B. Daly, M.D., Ph.D., director, Margaret Dyson Family Risk Assessment Program, Fox Chase Cancer Center, Philadelphia; Douglas F. Easton, Ph.D., Cancer Research UK and Genetic Epidemiology, Cambridge University, Cambridge, England; Feb. 9, 2004, International Journal of Cancer
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