Study suggests radiotherapy response is better among Black men versus White men with prostate cancer

The improved response to radiotherapy was observed despite Black men having more aggressive disease at enrollment.

Results from a meta-analysis performed at the UCLA Jonsson Comprehensive Cancer Center showed that among patients with prostate cancer who underwent radiation therapy (RT), Black men demonstrated higher success rates compared to White men.1,2

“Although previous studies have shown that death due to prostate cancer was similar for Black men and white men—provided there is equal access to care and standardized treatments—death from prostate cancer often is the culmination of many years of multiple salvage therapies, and prostate cancer mortality does not intrinsically capture initial responsiveness to primary therapy,” study author Ting Martin Ma, MD, PhD, explained in a new release.

“Here we studied early metrics of response to treatment, including biochemical recurrence (PSA rise above a threshold) or development of distant metastasis in men with localized prostate cancer, which is also the predominant disease state patients present with. This information will help us identify potential drivers and mitigators of disparities in prostate cancer care,” added Ma.

In this study, data were collected from 7 randomized clinical trials that were run by the NRG/Oncology/Radiation Therapy Oncology Group (RTOG) between January 1, 1990, and December 31, 2010. These trials assessed patients who underwent definitive RT with or without short- or long-term androgen deprivation therapy. The data of patients who self-identified as Black or White were extracted. Patients with node-positive disease were excluded from the assessment.

Of the 8814 enrolled patients, 18.5% (n = 1630) were Black and 81.5% (n = 7184) were White. The mean age of this population was 69.1 years, and for surviving patients, the median follow-up was 10.6 years (IQR, 8.0-17.8).

The primary end points were biochemical recurrence (BCR), distant metastases (DM), and prostate cancer-specific mortality (PCSM).

Unadjusted Fine-Gray competing risk models were used by investigators to estimate the cumulative incidences of endpoints, with death as the competing risk. In addition, Cox proportional hazard models and subdistribution hazard ratios (sHRs) were used to evaluate the association between race and endpoints.

Although black men showed higher high-risk disease features at enrollment, results before adjustment found that they were less likely to experience BCR (sHR, 0.88; 95% CI, 0.58-0.91), DM (sHR, 0.72; 95% CI, 0.58-0.91), or PCSM (sHR, 0.72; 95% CI, 0.54-0.97). Even after adjustment, there was still a significant association between Black patients and improved BCR (adjusted sHR, 0.79; 95% CO, 0.72-0.88; P <.001), DM (adjusted sHR, 0.69; 95% CI, 0.55-0.87; P = .002), and PCSM (adjusted sHR, 0.68; 95% CI, 0.50-0.93; P =.01).

“These results provide high-level evidence challenging the common belief that Black men who are diagnosed with prostate cancer will necessarily have a worse prognosis than white men,” said co-author Amar U. Kishan, MD. “This is especially important because an unfounded belief can inadvertently contribute to ‘cancer injustice,’ leading to the use of more aggressive treatments than might be necessary—potentially reducing quality of life—and diverting attention away from other important factors that can influence outcome, including access to more comprehensive healthcare.”

Other findings included no significant differences in time to all-cause mortality (HR, 0.99; 95% CI, 0.92-1.07) or other-cause mortality (sHR, 1.03; 95% CI, 0.95-1.12; P =.50).

Limitations were possible residual confounding from the post-hoc analysis, self-identification of race, and unstandardized post-BCR and post-DM salvage therapies. The investigators also did not have the ability to adjust the study based on data for other prognostic variables because it was unavailable.

In commenting on the overall results of the study, the authors concluded in their study, “These results do not suggest that there are no biological differences that might drive differences in prostate cancer incidence between racial groups. In fact, it is possible that the association with differential treatment response that is noted might be, at least in part, explained by differences in underlying biology.”

References

1. Ma TM, Romero T, Nickols NG, et al. Comparison of response to definitive radiotherapy for localized prostate cancer in Black and White men: A Meta-analysis. JAMA Netw Open. 2021;4(12):e2139769. doi:10.1001/jamanetworkopen.2021.39769

2. Study: Although they tend to be diagnosed with higher-risk prostate cancer, Black men undergoing radiation therapy have better outcomes than white men. December 29, 2021. Accessed January 7, 2022. https://www.uclahealth.org/news/study-although-they-tend-be-diagnosed-with-higher-risk