With Prostate Cancer, Race Is Not Entirely Black and White

Nick Mulcahy

June 02, 2018

CHICAGO — In results that counter expectations, American black men with advanced prostate cancer who received standard-of-care systemic therapy in clinical trials had equal outcomes with their white counterparts for overall survival in one study, and for disease progression in another.

The results are good news because of the dramatic disparity that otherwise exists in the United States, with black men much more likely to die from prostate cancer (and develop it) than white men.

The new results should serve as a reminder to clinicians to either enroll black men into clinical trials or to offer standard-of-care treatment, said Daniel J. George, MD, from Duke University in Durham, North Carolina. He was the lead author of a prospective study of 100 black and white men who were treated with abiraterone and prednisone for metastatic castrate-resistant disease and who had comparable rates of subsequent radiographic disease progression.

In the second study, Susan Halabi, PhD, also from Duke University, reported retrospective results from pooled data of nine randomized phase 3 trials of chemotherapy for advanced disease, totaling more than 8000 men. It is the largest study ever comparing outcomes among black and white men with lethal prostate cancer. The findings are encouraging: median overall survival was the same in black men and white men overall (21 months). However, only 6% of the study population was black; 85% was white.

Both studies were presented here at American Society of Clinical Oncology (ASCO) 2018 and were highlighted at a press briefing.

At the briefing, Halabi emphasized that her results were from clinical trials and were "not generalizable to the US population."

However, an ASCO expert, Robert Dreicer, MD, who was part of the press conference and is from the University of Virginia Cancer Center in Charlottesville, commented, "what this says to us is that when we treat African American men with prostate cancer, they do well."

Richard Schilsky, MD, ASCO chief medical officer, was also taken by the idea of access as a disparity equalizer: "The bottom line is, in a sense, that African American men with advanced prostate cancer need to get to an oncologist and ideally need to get on a clinical trial, and if they do, their outcomes are every bit as good as Caucasian men."

However, investigator Halabi is not convinced that racial disparities in prostate cancer will completely fall away with improved access to quality care.

"Enrollment in clinical trials may not necessarily eliminate everything because...there may be biological differences [between blacks and whites]," she said.

The cause of the racial disparities in prostate cancer in the United States are "multifactorial" and cannot be solved by improved access alone, said Curtis Pettaway, MD, from the University of Texas MD Anderson Cancer Center in Houston, who was asked for comment.

Pettaway described Halabi's study as "good news," saying, "in this study, black men with advanced prostate cancer treated with the appropriate systemic therapy at the appropriate time appear to have equal or better outcomes as white men."

But having a larger perspective is important, said Pettaway. Compared with white men, there is a 60% higher incidence of prostate cancer among black men, and the death rate from the disease is more than two times greater.

Furthermore, studies that suggest equal access results in equal outcomes do not get to the root of a racial disparity in prostate cancer that suggests important biological differences; namely, prostate cancer is diagnosed about 5 years earlier in blacks than whites. An example of this age-of-onset disparity includes men diagnosed at age 40 to 44 years: the prostate cancer incidence per 100,000 is 6.9 for white men and 19.9 for black men, said Pettaway.

"You can't make a sweeping statement about access — it's oversimplistic," he said, adding that both biology and social issues also influence disparities in prostate cancer.

You can't make a sweeping statement about access — it's oversimplistic. Dr Curtis Pettaway

For example, in terms of social issues, there is the problem of race bias, in which physicians will not prescribe the optimal therapy to black men, which contributes to poorer outcomes, he suggested. In contrast, there is the problem of some black men not trusting physicians to manage them appropriately and refusing certain treatments, which is also not optimal.

Lovell Jones, PhD, from the Texas A&M School of Public Health in Lubbock and professor emeritus at the MD Anderson Cancer Center, who was also approached for comment, likewise warned against looking at the two study results and making claims that equal access will ensure equal outcomes: "One to two studies does not make a theory," he said.

In addition, the analysis by Halabi and colleagues of overall survival among 8000 men in 8 clinical trials should not represent the future of research, said Jones, because it does not employ genomics.

"We need to start doing genomic testing to define the population you are looking at. It's time we entered the 21st century," he said.

Jones explained that some black Americans have ancestors from Europe, but that others will have a more predominant African ancestry, and this ancestry will determine their genetic make-up..

"When you look at who we classify as black in the United States, it runs the gamut. And if you look at their genetic make-up, it also runs the gamut," he told Medscape Medical News.

Prostate cancer in black men will eventually be shown to be just like triple-negative breast cancer in black women; that is, related to genetics, predicted Jones. He said the commonalities are that both have an early age of onset, are relatively more aggressive compared with those of white counterparts, and are linked genetically to specific areas in Africa that are also beset by the same cancers.

Thus, studies that compare black and white men's outcomes in prostate cancer are not optimal unless they define black Americans via genetic profiles because some black men are more African genetically than others, argued Jones.

However, another clinician, Willie Underwood, III, MD, MPH, from the Roswell Park Comprehensive Cancer Center, Buffalo, New York, who, similar to Pettaway and Jones, is black, echoed the views of the ASCO experts, who are white. "Regarding prostate cancer and black and white men, I think it true that equal treatment for equal disease results in equal outcomes," he told Medscape Medical News.

I think it true that equal treatment for equal disease results in equal outcomes. Dr Willie Underwood

Underwood is convinced that access to quality care is much more important than any other issue in terms of racial disparities. "The important question is not whether blacks and whites have different prostate cancers. The important question is whether or not we can cure or improve survival outcomes among men, no matter which prostate cancer they have," he said.

Furthermore, Underwood does not think much of the idea of biologically different prostate cancers among black men. "We must focus on optimizing the care of all men instead of using a theory of so-called bad black genes to justify doing nothing to end a social problem that is a plague on our healthcare system," he said.

More Study Details

Halabi and her team analyzed data from 8820 men with metastatic castration-resistant prostate cancer, all of whom received chemotherapy (docetaxel with prednisone) or a regimen containing the same combined with other therapies. The team hypothesized that the black men would have worse outcomes.

Despite the black men having worse prognostic factors overall, the median overall survival was the same among black men and white men, as noted here. In a multivariable analysis that adjusted for patient age, performance status, site of metastasis, prostate-specific antigen (PSA) level, and alkaline phosphatase and hemoglobin levels, the researchers found that black men were 19% less likely than white men to die from any cause (hazard ratio, 0.81; P = .004).

In the second study, known as Abi Race, George and colleagues enrolled 100 men with metastatic castration-resistant prostate cancer (50 white men and 50 black men). All the men received a standard treatment regimen, abiraterone acetate and prednisone, and were followed until disease worsened or adverse effects were intolerable. The study aimed to record responses and adverse effects by race.

Although time to radiographic disease progression, which was the primary outcome, was similar between the two groups, there was another outcome that favored black men: PSA kinetics, which is considered a marker of cancer response and progression but is not definitively correlated with overall survival. Black men had a median PSA progression-free survival of 16.6 months, which compared favorably with the 11.5 months in white men.

ASCO's Dreicer and Halabi, Jones, Underwood, and Pettaway have disclosed no relevant financial relationships. George has financial ties to multiple pharmaceutical companies, including Janssen, the makers of abiraterone, who also funded the Abi Race study.

American Society of Clinical Oncology (ASCO) 2018: Abstracts 5005 and 5009. Presented June 2, 2018.

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