Race-based difference in survival with sipuleucel-T therapy confirmed
medwireNews: Following treatment with the autologous cellular immunotherapy sipuleucel-T for metastatic castration-resistant prostate cancer (mCRPC), African–American men can expect to live longer than their Caucasian counterparts, indicates an analysis of the PROCEED registry.
These real-world data are in line with a post-hoc analysis of a placebo-controlled phase III trial that indicated a greater survival benefit with sipuleucel-T for the African–American subgroup relative to the overall cohort, say the study authors.
As reported in a poster by Oliver Sartor (Tulane Medical School, New Orleans, Louisiana, USA) and colleagues at the 2019 ASCO Annual Meeting in Chicago, Illinois, USA, the registry included 221 African–American and 1649 Caucasian men who received at least one infusion of sipuleucel-T. The groups differed significantly with respect to baseline prostate-specific antigen (PSA) levels and therefore, the current analysis was conducted among PSA-matched individuals.
In this subcohort, overall survival (OS) following sipuleucel-T therapy was significantly longer for the 219 African–American participants than for their 438 PSA-matched Caucasian counterparts, at a median of 35.3 and 25.8 months, respectively, and a hazard ratio (HR) for death of 0.70.
Of note, the use of life prolonging therapies after sipuleucel-T was comparable between African–American and Caucasian men, with a respective 78% and 74% of individuals receiving further treatment.
And multivariate analysis adjusting for factors such as age, bodyweight, and prior treatments confirmed the association between race and OS, with an HR for death in favor of African–American ethnicity.
The observed survival gain appeared to be largely driven by improvements in the two lowest quartiles of PSA levels. Specifically, median OS was 54.3 and 37.4 months for African–American and Caucasian men with PSA levels at or below 8.00 ng/mL, a significant difference giving an HR of 0.49. The corresponding values were 48.8 months, 30.9 months, and 0.54 in the subgroup with PSA levels over 8.00 ng/mL but no higher than 29.48 ng/mL. No such significant survival difference between the races was seen in the higher PSA quartiles.
Sartor and co-authors observe that recent research has shown such race-based differences in survival with other therapies, such as docetaxel.
But they add that “[t]his analysis marks the largest known racial difference in OS in response to any therapy for mCRPC, a finding with implications for both prostate cancer pathophysiology and cancer immunotherapy.”
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