Study Sheds Light on Effect of Type of Treatment on Race-based Differences in Prostate Cancer–Specific Survival

Alexander Putnam Cole, MD

Although Black men with prostate cancer had a higher cumulative incidence of prostate cancer–specific mortality than White men with the disease, when managed with the same treatment, they achieved similar survival outcomes, according to data from a retrospective study presented at the 2023 American Urological Association Annual Meeting. This may suggest that racial and ethnic disparities may be more attributable to unequal care and access to treatment, and should be addressed early in the disease course, according to Alexander Putnam Cole, MD.

In the study of non-Hispanic Black and non-Hispanic White men with localized intermediate- and high-risk prostate cancer, a comparison of cancer-specific survival according to race and treatment modality showed that Black men had a greater cumulative incidence of prostate cancer–specific mortality and were less likely to receive surgery over radiation vs White men (adjusted odds ratio, 0.53; 95% CI, 0.51-0.55; P < .001). Radiation was also linked with a higher risk of prostate cancer–specific mortality than surgery (adjusted HR [aHR], 2.03; 95% CI, 1.79-2.31; P < .001).

A model with an interaction term between race and treatment was utilized to evaluate whether the type of treatment mitigated or exacerbated racial disparities. Results did not reveal a difference in prostate cancer–specific mortality in Black vs White patients who received surgery (aHR, 1.25; 95% CI, 0.97-1.63; P = .086) or radiation (aHR, 0.95; 95% CI, 0.82-1.11; P = .056).

“This is consistent with other research that has been done by myself and my team, [which suggests] that equal access to care and equal treatment a lot of the racial differences in survival [to] go away,” said Cole, who is an assistant professor of surgery at Harvard Medical School, associate surgeon in the Division of Urological Surgery, at Brigham and Women’s Hospital, and junior core faculty at the Center for Surgery and Public Health in Boston, Massachusetts. “That [suggests that] differences in how people access care is a mediator of racial disparities in cancer outcomes.”

In an interview with OncLive^®, Cole discussed the importance of investigating racial and ethnic disparities in prostate cancer outcomes, key data from this analysis, and how these results could better inform efforts to improve access to, and quality of, patient care in this disease.

OncLive^®: Please describe the rationale for investigating the magnitude of race-based differences in cancer-specific survival between surgery and radiotherapy in patients with prostate cancer.

Cole: This is a study using the Surveillance, Epidemiology and End Results [SEER] cancer registry. We know that Black men are about twice as likely to die from prostate cancer, and that there are differences in the types of treatments that Black and White men receive [for their disease]. We also know that there are differences in the quality of the care that Black and White men receive for prostate cancer.

For example, White men are more likely to be referred to high-volume cancer surgeons regarding radiation for prostate cancer and are more likely to meet certain quality metrics for radiotherapy. The question that we had was whether the racial differences in outcomes arise within these two treatment modalities or predominantly arise between these two modalities or within these modalities. Furthermore, is there a bigger difference [between racial outcomes] with one of these treatments? For example, you might imagine that a surgeon’s expertise and surgical volume matters a lot in surgery, whereas radiation might be a bit more standardized. There might be a larger racial disparity seen in surgery compared with what you might see in radiation therapy.

What methods were used to conduct the analysis?

[We conducted] an unadjusted analysis, and then an adjusted analysis. We wanted to see whether there were racial differences in prostate cancer–specific mortality, and whether there were differences in the type of primary treatment for high-risk localized prostate cancer. We [initially] used 2 different regression models. One was for prostate cancer–specific mortality, and the other was for treatment with either radiotherapy or surgery. We then [used] a third regression model with an interaction term, which combined both race and treatment. That term tests whether a patient’s race modified the effect of different treatment modalities.

Could you discuss the key data from this study that were presented at the 2023 AUA Meeting?

When looking at the odds of prostate cancer–specific mortality, the hazard ratio was about 2. It was 2 times more likely for Black men to die from this type of prostate cancer. We know that; it’s not really a new finding. With regard to treatment, we found that the odds ratio for radiotherapy was about 1.8; that means that Black men were about 80% more likely to receive primary treatment with radiotherapy. The direction and the magnitude were both pointing toward more prostate cancer–specific mortality for Black men, and more radiotherapy for Black men; the magnitude of that was fairly similar. When we looked at the interaction between race and treatment, we found that this was not significant. It didn’t seem like race had a bigger effect in surgery vs a bigger effect in radiation therapy.

Interestingly, we then did a survival model where we included treatment. We no longer saw [a race-based difference in prostate cancer–specific mortality] when we adjusted for the type of treatment that these [patients received]. This has been shown in other work by our group like Dr. Krimphove’s 2019 in Prostate Cancer and Prostatic Diseases.

Do these findings elucidate the factors that contribute to racial disparities in clinical practice? At what point in the disease course should these be addressed?

The “cheap explanation” is that Black men are dying [at increased rates] because they’re getting radiotherapy, and [they appear to have] worse outcomes [with this modality]. I don’t think that’s the case. We don’t see that phenomenon in most [quality] research. That would be one potential interpretation, but I don’t think it’s quite right.

[These findings] do [suggest] that the disparities seem to start early on, [specifically] at the point of making a treatment decision. Once that treatment decision is made, there’s less of a racial difference when getting the treatment. This points to [the need for] efforts that are focused on access to care. Disparities start early; they start at the beginning of the diagnostic and treatment pathway. Once you get on that treatment pathway, from that point onward, those disparities are not as present. This is one of the major places where racial disparities in prostate cancer [originate].

Based on these findings, what steps is your institution taking to address the effect of racial disparities on prostate cancer outcomes?

We have something at [BWH and Massachusetts General Hospital] called the Prostate Cancer Outreach Clinic. I work at a very good, nationally ranked hospital with access to experienced surgeons and next-generation diagnostics. Many of my patients are affluent White men with prostate cancer, whereas men in minoritized communities in areas around Boston aren’t necessarily getting to our clinic. We don’t know exactly why. Maybe they get diagnosed and referred to a radiation center nearby without a multidisciplinary evaluation. Maybe there are transportation barriers. There are millions of potential factors and we have grant funding from the Department of Defense and American Cancer Society to identify and intervene on these barriers.

[In] our Prostate Cancer Outreach Clinic, [we’re] trying to build in an infrastructure that includes social workers, community outreach workers, community partners, and folks at community health centers, and create a pathway for these [patients] to access our hospital, our clinic, our surgeons, and our radiation oncologists. This is a small part of a larger United Against Racism program here at Mass General Brigham, and they’ve been very helpful in getting this off the ground.

Reference

Frego N, Labban M, Stone B, et al. MP77-17 Effect of type of definitive treatment on race-based differences in prostate cancer-specific survival. J Urol. 2023;209(4):e1109. doi:10.1097/JU.0000000000003351.17