Original Research

Impact of Race on Outcomes of High-Risk Patients With Prostate Cancer Treated With Moderately Hypofractionated Radiotherapy in an Equal Access Setting

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References

Results

We identified 143 patients with HRPC treated with definitive MHRT between November 2008 and August 2018 (Table 1). Mean age was 65 years (range, 36-80 years); 57% were African American men. Eighty percent of individuals had unfavorable high-risk disease. Median (IQR) PSA was 14.4 (7.8-28.6). Twenty-six percent had grade group 1-3 disease, 47% had grade group 4 disease, and 27% had grade group 5 disease. African American patients had significantly lower pre-MHRT IPSS scores than White patients (mean IPSS, 11 vs 14, respectively; P = .02) despite similar rates of preradiotherapy urinary medication usage (66% and 66%, respectively).

Patient Demographic Data by Race

Eighty-six percent received 70 Gy over 28 fractions, with institutional protocol shifting to 60 Gy over 20 fractions (14%) in June 2017. The median (IQR) duration of radiotherapy was 39 (38-42) days, with 97% of individuals undergoing ADT for a median (IQR) duration of 24 (24-36) months. The median follow-up time was 38 months, with 57 (40%) patients followed for at least 60 months.

Grade 3 GI and GU acute toxicity events were observed in 1% and 4% of all individuals, respectively (Table 2). No acute GI or GU grade 4+ events were observed. No significant differences in acute GU or GI toxicity were observed between African American and White patients.

Frequency of Acute Toxicity Events

No significant differences between African American and White patients were observed for late grade 2+ GI (P = .19) or GU (P = .55) toxicity. Late grade 2+ GI toxicity was observed in 17 (12%) patients overall (Figure 1A). One grade 3 and 1 grade 4 late GI event were observed following MHRT completion: The latter involved hospitalization for bleeding secondary to radiation proctitis in the context of cirrhosis predating MHRT. Late grade 2+ GU toxicity was observed in 80 (56%) patients, with late grade 2 events steadily increasing over time (Figure 1B). Nine late grade 3 GU toxicity events were observed at a median of 13 months following completion of MHRT, 2 of which occurred more than 24 months after MHRT completion. No late grade 4 or 5 GU events were observed. IPSS values both before MHRT and at time of last follow-up were available for 65 (40%) patients, with a median (IQR) IPSS of 10 (6-16) before MHRT and 12 (8-16) at last follow-up at a median (IQR) interval of 36 months (26-76) from radiation completion.

Clinical Outcomes Across Patient Race
Toxicity-Free Survival for African American and White Patients

No significant differences were observed between African American and White patients with respect to BRFS, DMFS, PCSS, or OS (Figure 2). Overall, 21 of 143 (15%) patients experienced biochemical recurrence: 5-year BRFS was 77% (95% CI, 67%-85%) for all patients, 83% (95% CI, 70%-91%) for African American patients, and 71% (95% CI, 53%-82%) for White patients. Five-year DMFS was 87% (95% CI, 77%-92%) for all individuals, 91% (95% CI, 80%-96%) for African American patients, and 81% (95% CI, 62%-91%) for White patients. Five-year PCSS was 89% (95% CI, 80%-94%) for all patients, with 5-year PCSS rates of 90% (95% CI, 79%-95%) for African American patients and 87% (95% CI, 70%-95%) for White patients. Five-year OS was 75% overall (95% CI, 64%-82%), with 5-year OS rates of 73% (95% CI, 58%-83%) for African American patients and 77% (95% CI, 60%-87%) for White patients.

Discussion

In this study, we reported acute and late GI and GU toxicity rates as well as clinical outcomes for a majority African American population with predominately unfavorable HRPC treated with MHRT in an equal access health care environment. We found that MHRT was well tolerated with high rates of biochemical control, PCSS, and OS. Additionally, outcomes were not significantly different across patient race. To our knowledge, this is the first report of MHRT for HRPC in a majority African American population.

We found that MHRT was an effective treatment for patients with HRPC, in particular those with unfavorable high-risk disease. While prior prospective and randomized studies have investigated the use of MHRT, our series was larger than most and had a predominately unfavorable high-risk population.12,15-17 Our biochemical and PCSS rates compare favorably with those of HRPC trial populations, particularly given the high proportion of unfavorable high-risk disease.12,15,16 Despite similar rates of biochemical control, OS was lower in the present cohort than in HRPC trial populations, even with a younger median age at diagnosis. The similarly high rates of non–HRPC-related death across race may reflect differences in baseline comorbidities compared with trial populations as well as reported differences between individuals in the VA and the private sector.31 This suggests that MHRT can be an effective treatment for patients with unfavorable HRPC.

We did not find any differences in outcomes between African American and White individuals with HRPC treated with MHRT. Furthermore, our study demonstrates long-term rates of BRFS and PCSS in a majority African American population with predominately unfavorable HRPC that are comparable with those of prior randomized MHRT studies in high-risk, predominately White populations.12,15,16 Prior reports have found that African American men with HRPC may be at increased risk for inferior clinical outcomes due to a number of socioeconomic, biologic, and cultural mediators.26,27,32 Such individuals may disproportionally benefit from shorter treatment courses that improve access to radiotherapy, a well-documented disparity for African American men with localized prostate cancer.33-36 The VA is an ideal system for studying racial disparities within prostate cancer, as accessibility of mental health and transportation services, income, and insurance status are not barriers to preventative or acute care.37 Our results are concordant with those previously seen for African American patients with prostate cancer seen in the VA, which similarly demonstrate equal outcomes with those of other races.28,36 Incorporation of the earlier mentioned VA services into oncologic care across other health care systems could better characterize determinants of racial disparities in prostate cancer, including the prognostic significance of shortening treatment duration and number of patient visits via MHRT.

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