Evaluation of factors predicting response to abiraterone acetate in metastatic castration-resistant prostate cancer: A prospective study

Abstract

Background/Objectives: In the current era, abiraterone acetate is mainstay of the treatment strategies of castration-resistant prostate cancer and proven to prolong overall survival. We aimed to prospectively identify factors associated with duration of response to abiraterone. Patients and methods: All metastatic castration-resistant prostate cancer patients eligible for abiraterone were included in the study from February 2019 till March 2020. All baseline data and potential factors associated recorded and follow-up with prostate-specific antigen (PSA), and required investigations were done at 1 month interval. Duration of PSA response was recorded, and patients were divided in five groups on the basis of duration of response. Univariate and multivariate analyses of potential factors were done, and data analysis was done with SPSS (Statistical Package for the Social Sciences) version 21.0. Results: In this study, after univariate analysis, seven factors were associated with longer duration of response to abiraterone. These were PSA at diagnosis (hazard ratio (HR) = −1.011 (95% confidence interval (CI) = 1.003–1.020), p-value = 0.008), PSA at start of abiraterone (HR = −1.018 (95% CI = 1.011–1.025), p-value = 0.0001), nadir PSA (HR = −1.063 (95% CI = 1.024–1.104), p-value = 0.001), prostate-specific antigen doubling (PSAD) time (HR = −0.745 (95% CI = 0.672–0.827), p-value = 0.001), raised alkaline phosphatase (ALP) (HR = −1.002 (95% CI = 1.001–1.003), p-value = 0.001), neutrophil/lymphocyte ratio (NLR) (HR = −2.16 (95% CI = 1.672–2.81), p-value = 0.001) and <5 bone metastasis (HR = −0.235 (95% CI = 0.130–0.422), p-value = 0.01). But after multivariate analysis, nadir PSA achieved, PSAD, NLR and ⩽5 bone metastasis were predictors of better response to abiraterone. Conclusion: This study had identified that less nadir PSA achieved, long PSAD time, low NLR and limited number of skeletal metastases were potential factors for better PSA response to abiraterone. Level of evidence: 1