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Testicular cancer is the most common malignancy among young men ages 15 to 35, with approximately 7,400 cases diagnosed annually in the U.S. A few clear risk factors exist, including cryptorchidism (undescended testicle), a prior history of cancer in one testicle (the opposite testicle is at increased risk), and other rare conditions where the testes develop abnormally. Among those men diagnosed with testicular cancer, about 1-3 percent report a family history of the disease. Brothers of affected individual are 8 to 10 times more likely to develop testicular cancer, and men whose fathers had testicular cancer are four times more likely to develop testicular cancer, when compared with the relatives of men who have never had testicular cancer. While some genetic clues are starting to emerge, the gene(s) that cause testicular cancer have yet to be discovered.

Clinical researchers from 14 different countries have banded together in an effort to find the gene(s) involved in causing familial testicular cancer. They have formed an organization called the International Testicular Cancer Linkage Consortium (ITCLC), and pooled the information collected from the families they each identified, to do a systematic search for these genes. In 2000, these investigators published evidence that a familial testicular cancer gene might be located on the X-chromosome, and they proposed that this might explain the higher risks in some families, especially those families in which at least one of the affected men had bilateral testicular cancer (EA Rapley et al: Nature Genetics 2000; 24:197-200). This candidate gene has been named the Testicular Germ Cell Tumor-1 (TGCT1) gene, and efforts to further refine the chromosomal location and determine the DNA structure of the gene are now underway. The gene itself has not yet been identified.

Studying high-risk families is the major way of identifying genes that cause diseases, and this strategy provides unique opportunities to examine other risk factors as well. Under the leadership of Mark H. Greene, M.D., the Clinical Genetics Branch (CGB) at the National Cancer Institute in Bethesda, MD has recently begun to actively recruit new families. Criteria for enrollment into the study include at least one of the following: 1) two or more men in the family have testicular cancer, 2) one family member has bilateral testicular cancer (that is, separate cancers involving both testicles), or 3) one family member with testicular cancer is a member of a set of genetically identical brothers, such as twins or triplets. Since multiple-case testicular cancer families are relatively rare, Dr. Greene and his colleagues have been contacting both physicians and testicular cancer support/advocacy organizations, in an effort to identify additional families.

As part of its research strategy, the NCI study team has joined the International Testicular Cancer Linkage Consortium. The Clinical Genetics Branch is contributing genetic material (DNA) collected from the new families it has identified to this international research effort. The goal is to assemble a large enough group of high-risk families to permit locating the proposed gene on the X chromosome, and perhaps finding other genes as well. Eventually, it is hoped that this research will lead to the development of laboratory tests to identify individuals who are at increased genetic risk of testicular cancer.

The CGB team also hopes to make significant contributions to understanding the full spectrum of the hereditary testicular cancer syndrome. In addition to helping identify the gene or genes that cause familial testicular cancer, they hope to better describe its clinical features, explore whether these families are at a higher risk of other cancers, perform the first systematic review of the pathology of familial testicular cancers, examine the emotional and psychosocial issues affecting family members, develop better health care choices for at risk individuals, and create a repository of biological specimens to be used in various laboratory studies intended to help us learn more about how testicular cancer develops.

Families may participate either by providing questionnaire information and blood samples from their home communities, or they may travel to the NIH Clinical Center for an in-person evaluation. Expenses related to coming to the NIH, and the costs involved in participating in the study, are covered by the study's budget.

More information on the study can be found online at: http://familial-testicular-cancer.cancer.gov.



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