Researchers hope to develop a better way to identify men at high risk for prostate cancer

January 16, 2007

(SACRAMENTO, Calif.) — A new study under way at UC Davis Cancer Center may help doctors see beyond skin color when it comes to decisions about prostate-cancer screening and treatment for African-American men.

The “Diet and Ancestry Study of Prostate Cancer Among African-Americans” will analyze blood samples from 100 African-American volunteers living in the Sacramento area for genetic markers of European and African ancestry.

As a group, African-American men are twice as likely as white men to develop prostate cancer, and twice as likely to die of the disease.

However, UC Davis Cancer Center researchers expect to find that not all black men have the same prostate cancer risk. The researchers hypothesize that African-Americans of predominantly European ancestry will have a lower prostate-cancer risk than those of predominantly African ancestry.

Several other diseases, including type 2 diabetes and systemic lupus erythematosus, are also linked with African ancestry.

“It's been assumed that all men who self-identify as African-American are at equal risk of developing prostate cancer. Now we can look at this in more detail,” said Ralph deVere White, director of UC Davis Cancer Center and urological investigator for the study.

The researchers will look for genetic markers called Ancestry Informative Markers, which can be used to estimate the African and European contributions to the genetic makeup of an individual. The genetic analysis will be overseen by Michael Seldin, professor and chair of the Rowe Program in Genetics.

The study promises to better enable physicians to determine which patients, for example, should begin early PSA testing. PSA testing measures levels of a protein known as prostate-specific antigen in the blood. The protein is a marker for prostate cancer. The American Cancer Society and other groups recommend that most men begin getting annual PSA tests starting at age 50. High-risk men are advised to begin PSA testing at age 40.

“Measuring genetic ancestry could help prevent invasive screening when it's not necessary and more properly identify those who need aggressive screening and surveillance,” said Lesley Butler, an assistant professor of public health sciences and the study's principal investigator.

The study will also look at non-genetic factors, such as diet, tobacco use and medical history. De Vere White acknowledged there are concerns about risk categorization based on genetic analysis. But he said the role of genes in cancer susceptibility is simply too powerful to ignore.

The National Cancer Institute, in its recent report, “Accelerating Successes Against Cancer,” also emphasizes the importance of research to more precisely identify populations with genetic predispositions to particular malignancies, as a first step toward designing screening, chemopreventive and other strategies to reduce these risks and save lives.

Among the first volunteers to enroll in the UC Davis study was Roger Brown, a 64-year-old retired bail bondsman from Sacramento who was diagnosed with prostate cancer two years ago. Like Brown, half of the study participants will have a prostate cancer diagnosis. The other half will serve as controls.

Brown said part of his motivation for participating is simply to learn about his heritage, knowledge that has been unavailable to many African-Americans. But he also hopes his participation will save lives. “The more knowledge we have about this disease, the better,” Brown said.

For information about volunteering for the study, please contact Michele Castillo at (916) 734-8138.