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ASCO 2021

ASCO 2021: Prostate Cancer: Rejecting the Biologic Basis for Outcome Disparities

(UroToday.com) We know from SEER data that black men are 1.7x more likely to be diagnosed with prostate cancer and are 2.1x more likely to die from their prostate cancer. This is not new data, as these trends were evident in the 1950s and 1970s as well but appear to be worsening in severity. This has led to the perception that race is an independent prognostic factor associated with worse prostate cancer outcomes. This is reflected in guidelines from the AUA/ASTRO/SUO that advise counseling patients on their individualized risk of disease recurrence based on clinical factors and patient race. Thus, race is thought to be a proxy for ancestral genetics that are related to worse prostate cancer health outcomes.


Dr. Robert Dess argues that the reality is that race is a social construct. Across all cancers tracked by SEER, black patients have the highest cancer-associated mortality relative to other races. This is paralleled by data showing black people have higher rates of poverty and unemployment as well as mortality from diabetes and heart disease. In the COVID-19 pandemic, black people diagnosed with COVID had a 1.9x risk of death from this disease. He suggests that what is also really being measured is the effects of structural racism that impact other factors including tumor biology such as access to high-quality healthcare and the means to pursue healthy interventions that affect health outcomes. This is not a novel idea. Dr. Dess quoted an editorial from Rivara and Finberg in 2001 that stated “Many studies in which race or ethnicity is mentioned as an explanatory variable are attempting to instead measure other individual or population characteristics such as education, household income or poverty. Unfortunately, race and ethnicity are poor proxies for the variables of interest.”

Back to prostate cancer, it is known that black men are diagnosed with a larger burden of disease and higher stage despite similar risk profiles. To further assess the association between black race and prostate cancer mortality, Dr. Dess summarized a recent publication of his examining outcomes of black men in three cohorts:1 (1) A SEER cohort of 52,000 black men, (2) a VA cohort of over 1500 black men, and (3) An individual patient meta-analysis of over 1500 black men from RTOG trials. Using a competing risk model, as more variables were weighted along with race, the difference in 10-year prostate cancer-specific mortality between black and white patients became much smaller, and in the smaller cohorts that arguably offered more equal access to care (the VA, randomized controlled trials), the difference trended towards black patients having slightly lower prostate cancer-specific mortality.

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This is also not an entirely new finding. Data published in 2003 from four RTOG trials including over 2,000 men from the 1970s to 1990s2 also found no independent association between race and outcome in clinically localized prostate cancer when controlling for other variables such as age and stage. In advanced prostate cancer, Halabi and colleagues3 found that when adjusting for other prognostic factors, black patients treated with docetaxel chemotherapy had a statistically significant improved overall survival relative to white patients. Furthermore, in a prospective trial of abiraterone acetate in black and white men with metastatic castration resistant prostate cancer, Dr. George and colleagues found similar rPFS and OS rates between the two groups. Across all cancers, published literature from almost twenty years4 ago examining survival rates in black and white patients suggested that differences in cancer biology are unlikely to be responsible for a substantial portion of observed survival discrepancy between races.

Dr. Dess concluded his talk by stating that discrepancies by race for cancer survival are real. Race, however, is a social construct and data suggests that equitable outcomes are possible for patients. Equity is a complicated concept to execute and measure, but cancer care must make and continue to make equity a major focus.

Presented by: Robert Timothy Dess, MD, Clinical Assistant Professor and Radiation Oncologist at the University of Michigan, Ann Arbor, MI

Written by: Alok Tewari, MD, PhD, Medical Oncologist at the Dana-Farber Cancer Institute, at the 2021 American Society of Clinical Oncology (ASCO) Annual Meeting, Virtual Annual Meeting #ASCO21, June, 4-8, 2021

References:

  1. Robert T. Dess, Holly E. Hartman, Brandon A. Mahal, et al. "Association of Black Race With Prostate Cancer–Specific and Other-Cause Mortality." JAMA Oncol. 2019;5(7):975-983.
  2. Roach M 3rd, Lu J, Pilepich MV, et al. Race and survival of men treated for prostate cancer on radiation therapy oncology group phase III randomized trials. The Journal of Urology. 2003 Jan;169(1):245-250.
  3. Halabi S, Dutta S, Tangen C.M, Overall Survival of Black and White Men With Metastatic Castration-Resistant Prostate Cancer Treated With Docetaxel. Journal of Clinical Oncology. 2019 Feb;37(5): 403-410.
  4. Peter B. Bach, Deborah Schrag, Otis W. Brawley, et al. "Survival of Blacks and Whites After a Cancer Diagnosis." JAMA. 2002;287(16):2106-2113.