Study points to race-based difference in prostate cancer progression
June 2, 2020
VA Research Communications
"African American men with low-risk prostate cancer are more likely to have undetected higher-grade cancer that could put them at risk for cancer recurrence."
A study of VA patients with low-risk prostate cancer found no differences between African American and white men for many outcomes. However, African American men whose biopsies showed low-risk cancer were more likely to have a higher grade or stage of cancer when they were later treated surgically.
“African American men with low-risk prostate cancer are more likely to have undetected higher-grade cancer that could put them at risk for cancer recurrence,” says senior study author Dr. Brent Rose.
The results suggest that African American men with low-risk prostate cancer may need additional evaluation before they and their doctors decide to wait on treatment and manage the condition only with active surveillance, according to the VA San Diego Health Care System and University of California San Diego School of Medicine researchers.
The results appeared April 23, 2020, in Prostate Cancer and Prostatic Diseases.
Many men with low-risk prostate cancer undergo active surveillance to manage the condition. Active surveillance involves closely monitoring prostate cancer for changes without direct cancer treatment. The method is used for many men with early-stage prostate cancer because the treatments—surgery or radiation treatment—come with their own risks. "Active surveillance is the preferred treatment option for many men with low risk prostate cancer in order to avoid or delay the side effects of radical prostatectomy or radiation therapy," according to Dr. Rishi Deka, first author on the study. The most common side effects of these treatments are urinary incontinence, erectile dysfunction, rectal bleeding, and painful bowel movements, says Deka. Many prostate tumors are slow-growing, meaning that these men may do fine—or eventually die of other causes—even if they forgo treatment.
But some studies have shown that African American men may be at greater risk for higher-stage prostate cancer. This risk may mean they are not good candidates for active surveillance. It is also not known whether the poorer prostate cancer outcomes seen in African American men are because of biological differences or because of disparities in access to health care—or some combination.
To explore this difference, the researchers studied nearly 3,000 men with low-risk prostate cancer. All of the men were treated with radical prostatectomy, surgical removal of the prostate gland, and were followed for about seven years after the surgery.
All patients were treated in the VA health care system, an equal-access system where socioeconomic status tends to have far less influence on care access than in U.S. medical care generally. This means that African American and white patients had access to the same cancer care. "The VA health care system may reduce barriers to care that still exist for African American men in other health care settings," explains Deka. "Examples of these reduced barriers include exemptions from medication copayments, access to health care at non-VA hospitals, and increases in staffing and facilities at existing VA medical centers." According to Deka, VA provides a "robust setting" to investigate whether health disparities are based on access to care or biological differences.
All the men’s prostate cancer was classified as low-risk using several biological factors. Tumors were given a Gleason score, a rating of the how widespread and abnormal cancer cells are in a biopsy. They were also rated by clinical tumor grade, a separate measure of the extent of the cancer. Finally, the researchers measured prostate-specific antigen (PSA), an enzyme secreted by the prostate gland. This enzyme is often elevated in men with prostate cancer.
Differences seen in rate of cancer spread
For most of the measures, the researchers did not see any differences based on race in how the condition changed over time. The rates of higher clinical tumor grade and increased PSA concentrations were similar between African American and white patients. The mortality rate was also similar for both groups.
However, African American men were more likely to be reclassified from Gleason grade group 1, the least dangerous stage of prostate cancer, to group 2, meaning their cancer was more widespread. There were no differences between African American and white men in moving from group 2 to group 3. The Gleason grade group ranks how widespread cancer cells are from 1 to 5, with 1 meaning the prostate cells look close to normal healthy cells and 5 meaning the tissue is the most abnormal and the cancer cells are widespread.
Rose and his team believe that one explanation for the findings might be that “the higher grade disease was always there and the biopsy missed it for some reason.” In other words, the African American men in the study may have started out with higher-grade cancer, but their tumors were somehow harder to evaluate, and therefore ended up getting misclassified as low-risk when they were actually more aggressive.
Caution with regard to active surveillance option
Because African American men were more likely to have undetected high-risk cancer, they may have done worse if treated only with active surveillance, according to Rose. “While the men in the study all underwent prostatectomy, it is not clear if outcomes would have been as favorable if they had undergone active surveillance instead,” he says.
According to the researchers, “The implication is that African American men may need to undergo additional evaluation … before initiating active surveillance.” If these patients are at high risk for more dangerous prostate cancer, they may need more aggressive treatment, rather than active surveillance.
The researchers also suggest further studies to look at what causes poorer long-term outcomes in African American men with prostate cancer. While this question has long been looked at by researchers, it is still unclear whether poorer outcomes in African American patients are related to health care disparities or genetic or other biological differences, or a mix of both types of factors. Because the study took place in the VA health care system, which offers patients equal access to care, the results suggest that the disparity has some basis in biology, say the researchers.