Black men diagnosed with low-risk prostate cancer are two times more likely to actually have a more aggressive, fatal form of the disease than those of other races, suggesting that the current prostate cancer score method may be underestimating the risk of death among black patients, a study suggests.
The study, “Prostate Cancer–Specific Mortality Across Gleason Scores in Black vs Nonblack Men,” published in JAMA, also raises questions on whether the biology of low-risk prostate cancer in black men is different from that of other ethnic populations.
The Gleason score is one of the best predictors of outcomes for prostate cancer patients and can be used to determine appropriate treatment. Typically, patients with a Gleason score of six or less don’t necessarily need treatment — although some opt for it anyway — whereas Gleason scores from seven to 10 are indicative of especially aggressive cancer that requires more aggressive treatment, such as surgery.
Yet predictive models like the Gleason score are often imperfect, and they can sometimes under-perform for specific demographic groups.
“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,” Brandon Mahal, MD, first author of the report and a scientist in the department of radiation oncology at the Dana-Farber Cancer Institute, said in a press release.
The investigators compared outcomes for 192,224 men with prostate cancer, including 31,841 black patients and 160,383 nonblack patients, who were predominantly white, but also included other races.
Death rates between blacks and nonblacks didn’t differ. Death rates were also comparable among races for those with a Gleason score between seven and 10.
However, there was a noteworthy difference for patients with a Gleason score of six: The death rate after a median follow-up of 36 months was nearly twice as high in black patients — 0.40% vs. 0.22%.
The researchers then analyzed a larger group, including 62,736 black and 340,286 nonblack patients, for a longer follow-up time (12 years). Again, the same trend was found: There was no difference for patients with a Gleason score between seven and 10, but death rates were significantly different for those with a Gleason score of six — 2.2% for black versus 1.4% for nonblack patients.
In other words, black men diagnosed with low-risk cancer are more likely than men of other races to actually have more aggressive cancer that can be fatal, even after adjusting for socioeconomic status.
“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,” Mahal said, also noting that “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 non-tumor related factors such as how we perform the biopsies — maybe we are undersampling their tumors and missing more aggressive disease — and lastly there could be other socioeconomic or access to care factors that drive differences.”