Gleason 6 Score May Underestimate Prostate Cancer Mortality Risk in Black Men
Black men diagnosed with prostate cancer classified as low risk may actually have a more aggressive form of the disease that is more likely to be fatal than in nonblack men placed in the same prognostic category, according to results from a new study published as a research letter by Mahal et al in JAMA.
Study Methods
The study analyzed databases (Surveillance, Epidemiology, and End Results [SEER] Prostate Active Surveillance/Watchful Waiting [AS/WW]) of hundreds of thousands of men diagnosed with prostate cancer and assigned a Gleason score on the basis of a biopsy and examination of samples of the cancer under a microscope. The study findings focused on men who were classified as Gleason 6, which signifies a favorable prognosis with a low risk of death. Many men in this category, after a conversation with their doctor, adopt an “active surveillance” approach—but some men with Gleason 6 cancers opt for treatment rather than surveillance.
Findings
The study found that the overall risk of prostate cancer death was not statistically significant between 31,841 black and 160,383 nonblack patients, after accounting for socioeconomic status and treatment patterns. However, when the analysis focused on patients with Gleason grade 6 cancer, there were 51 deaths among 12,707 black patients (0.40%) vs 155 deaths among 70,938 nonblack patients (0.22%) at a median follow-up of 36 months.
The researchers did a similar analysis in a larger cohort of 62,736 black and 340,286 nonblack men who had been followed for a longer period. The 12-year prostate cancer mortality rate in patients with Gleason scores 7 to 12 was 5.5% in black men vs 5.3% in nonblacks. Again, a disparity appeared in Gleason 6 prostate cancers: the 12-year mortality rate was 2.2% in black patients vs 1.4% in nonblack patients. This difference, the authors wrote, “support the hypothesis that low-grade prostate cancer may be distinct in black men.”
Commentary
“Data suggests that African American men who have surgery for Gleason 6 cancers are more likely to have more aggressive surgical features than predicted prior to surgery than nonblack men having surgery,” said Brandon Mahal, MD, of the Department of Radiation Oncology at Dana-Farber Cancer Institute and first author of the report. While the reasons for this aren’t clear, he said, “the reasons are likely multifactorial—it could be that Gleason 6 cancer in black men is inherently more aggressive or it may have to do with other nontumor related factors, such as how we perform the biopsies…lastly, there could be other socioeconomic or access to care factors that drive differences.”
Asked what the study results imply for clinical practice, Dr. Mahal said, “These data would be an impetus for randomized, prospective trials to both better characterize Gleason 6 disease in black men and to test different management strategies,” ie, immediate treatment vs active surveillance. He said that in the United States, data suggest that an increasing number of men with Gleason 6 prostate cancer are opting for active surveillance, but that option is used less frequently among black men. “That probably is partly because of provider preferences and partly because of patient preferences—both of which are likely impacted by historically observed disparities,” said Dr. Mahal.
Franklin Huang, MD, PhD, of the University of California, San Francisco, is the corresponding author of the JAMA report.
Disclosure: The research was supported by the Prostate Cancer Foundation, the American Society for Radiation Oncology, and the Department of Defense Prostate Cancer Research Program. The study authors’ full disclosures can be found at jamanetwork.com.
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
