Black men are twice as likely to die of prostate cancer as white men. Government scientists said Tuesday that they are launching a study to try to discover why.

The aim is to gather samples from 10,000 prostate cancer patients to see if genes, stress, segregation or other factors account for the higher rates of the disease in African-American men, the National Institutes of Health said.

“Understanding why African-American men are more likely to be diagnosed with aggressive prostate cancer than men of other racial and ethnic groups is a critical, unanswered question in cancer disparities research,” Dr. Ned Sharpless, director of the National Cancer Institute, said in a statement.

The $26.5 million study, part of the Obama administration’s 21st Century Cures Cancer Moonshot initiative, will be a joint effort among the National Cancer Institute and the National Institute on Minority Health and Health Disparities, both part of NIH institutes, as well as the Prostate Cancer Foundation.

Prostate cancer is diagnosed in about 164,000 American menevery year. It kills about 29,000 a year, according to the American Cancer Society.

“African-American men have about a 15 percent chance of developing prostate cancer in their lifetimes, compared to about a 10 percent chance for white men, and African-American men are more likely to be diagnosed with aggressive disease,” the NIH said in a statement.

“In addition, the risk of dying from prostate cancer for African-American men is about 4 percent compared to about 2 percent for white men.”

Any number of factors could explain the differences, said Damali Martin, who will help direct NCI’s work on the study. “The ability to integrate genetic and environmental factors, including individual, neighborhood and societal factors, into one large study will enable us to have a better understanding of how all of these factors contribute to the aggressiveness of prostate cancer,” Martin said in the statement.

The team will find the 10,000 participants using cancer database information.

“No group in the world is hit harder by prostate cancer than men of African descent, and to date, little is known about the biological reasons for these disparities, or the full impact of environmental factors,” said Dr. Jonathan Simons, CEO of the Prostate Cancer Foundation.