Low-income men treated for prostate cancer are likelier to have a more aggressive disease at diagnosis compared with their better-off counterparts, a study at one U.S. public hospital suggests.

Researchers found that compared with prostate cancer patients seen at U.S. academic medical centers and private practices, an elevated rate of higher risk prostate cancer was seen among men treated at San Francisco General Hospital -- a publicly funded safety net hospital that primarily serves the low-income and uninsured.

The greater proportion of high-risk cancers could not be explained away solely by later diagnoses due to a lack of screening. The researchers speculate several factors may be at work.

High-risk prostate cancer refers to tumors that have an increased likelihood of spreading and becoming life threatening - because they are relatively extensive or have abnormalities that make them particularly aggressive, for instance.

Most prostate tumors are slow-growing, and may never advance far enough to shorten a man's life. This means that many men diagnosed with the disease can choose to forgo treatment in favor of periodic tests to monitor the cancer's progression. But prompt treatment, with surgery, radiation or other therapies may be recommended for men with higher risk prostate cancer.

MORE DANGEROUS TUMORS

In the current study, researchers found that of 377 men diagnosed with prostate cancer at the San Francisco public hospital between 1998 and 2008, only 29 percent had low-risk disease -- based on the stage of the tumor, blood levels of prostate-specific antigen (PSA) and Gleason score, a measure of the tumor's aggressiveness.

In contrast, low-risk cancer was found in about 39 percent of men included in two large prostate cancer databases -- one of patients treated at 31 U.S. academic medical centers and community-based practices since 1995, and one of men treated at the University of California, San Francisco (UCSF) between 1997 and 2007.

The rest of the men treated at San Francisco General Hospital - 61 percent -- had either high- or intermediate-risk prostate cancer, or had tumors that had already spread beyond the prostate.

Of men at the public hospital, 12 percent had cancer that had spread to the seminal vesicles outside the prostate gland, nearby lymph nodes or beyond.

That compared with roughly 4 percent in the national database and just under 7 percent in the UCSF registry, the researchers report in the Journal of Urology.

What's driving this? Right now, it's up in the air, said senior researcher Dr. Matthew R. Cooperberg, an assistant professor of urology at UCSF, in an interview.

The difference does not appear to be explained by disparities in access to medical care, Cooperberg told Reuters Health. He noted that many men at the public hospital had undergone routine prostate cancer screening.

Black men are at higher risk of prostate cancer than other racial groups, and the San Francisco General Hospital group had a larger percentage of African Americans than the two databases used for comparison.

However, Cooperberg said, racial differences do not appear to fully account for the greater burden of intermediate- to high-risk cancer among lower income men.

California Medicine Cancer