The findings, to be published in Wednesday's (Nov. 19) issue of the Journal of the National Cancer Institute, also show the greatest disparity to be among men who undergo surgery.
The study's lead author is Dr. Paul Godley, associate professor of medicine and epidemiology at the University of North Carolina at Chapel Hill, member of the UNC Lineberger Comprehensive Cancer Center and leader of the UNC Program on Ethnicity, Culture and Health Outcomes. He was joined by researchers from UNC's schools of medicine and public health, the Medical Review of North Carolina and Massachusetts General Hospital.
The study involved 5,747 black men and 38,242 white men with clinically localized prostate cancer. Researchers found that among those who had surgery, the median survival time for black patients was 1.8 years less than for white patients (10.8 years versus 12.6 years, respectively).
The differences in median survival times between black and white patients were smaller among patients treated with radiation therapy ( .7 years) and among patients who had non-aggressive therapy, also called "watchful waiting" (1.0 years).
About 75 percent of the estimated 189,100 prostate cancers diagnosed nationwide in 2002 were clinically localized at the time of diagnosis, so any disparities in outcomes among such patients are of great interest, Godley said. Clinically localized cancer is disease confined to the prostate.
Scientists merged the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) data with Medicare file information to compile their findings.
"Previous research into prostate cancer outcome disparities assumed that patients receiving similar treatment would have similar medical outcomes," said Godley. "We felt it was important to examine whether black and white patients treated with surgery or other treatments actually had similar survival. The disparities in survival persisted even after adjusting for geographic region where the patient was treated, tumor grade, other medical conditions and socio-economic factors.
"Figuring out why survival among blacks is worse and why surgical patients have the largest disparity will take more research."
Several reasons could account for these disparities, researchers said. One is that black patients had reduced access to specialized radiation therapy, which is preferred over surgery for patients in whom locally advanced cancer is suspected. Another possible explanation is genetic differences between races in response to prostate cancer treatment.
Their report concluded that "researchers should continue to investigate racial disparities in treatment outcomes as well as the specific social, biologic or environmental conditions that may be responsible for these disparities."
Funding was provided by the U.S. Centers for Disease Control and Prevention, the Association of Teachers of Preventive Medicine and the National Center on Minority Health and Health Disparities.
Note: Contact Godley at 919-218-7240 after 5 p.m. today (Nov. 18) or at pgodley@med.unc.edu.
Lineberger Center contact: Dianne Shaw, 919-966-7834
Journal
JNCI Journal of the National Cancer Institute