Systemic immune‐inflammation index predicts the combined clinical outcome after sequential therapy with abiraterone and docetaxel for metastatic castration‐resistant prostate cancer patients

Objective To compare the antitumor effect of abiraterone (AA) followed by docetaxel‐prednisone (DP) or vice versa in metastatic castration‐resistant prostate cancer (mCRPC) patients, and explored factors that might predict combined PSA‐PFS, combined rPFS and OS. Patients and Methods We retrospectively analyzed mCRPC patients treated with sequential therapy using DP followed by AA or vice versa. Patients who had received enzalutamide or cabazitaxel were excluded. The primary outcome measure was overall survival (OS). The combined PSA progression‐free survival (PSA‐PFS), combined radiographic PFS (rPFS), and OS of AA‐to‐DP were compared to the reverse sequence using Kaplan‐Meier curves with log‐rank statistics. Univariable and multivariable Cox regression analyses were performed to determine prognostic factors that were associated with combined PSA‐PFS, combined rPFS and OS. Results A total of 104 mCRPC patients who began treatment between 2013 and 2017 were identified: 42 were in the DP‐to‐AA group and 62 were in the AA‐to‐DP group. There was no significant difference of baseline clinical characteristics between AA‐to‐DP and DP‐to‐AA group. In addition, there was no significant difference in combined PSA‐PFS (AA‐to‐DP: 12.5 [11.4‐13.6] vs DP‐to‐AA: 13.2 [10.9‐15.5] months [P = 0.127]), combined rPFS (AA‐to‐DP: 12.2 [10.9‐13.4] vs DP‐to‐AA: 11.2 [8.9‐13.5] months [P = 0.183]) and OS (AA‐to‐DP: 23.3 [19.7‐26.9] vs DP‐to‐AA: 22.9 [22.1‐23.7] months [P = 0.213]) between the two treatment sequences in Kaplan‐Meier analysis. In multivariate Cox regression analysis, high systematic Immune‐Inflammation Index (SII) level, which was calculated by P (platelet) × N (neutrophil)/L(lymphocyte), remained significant predictors of OS, combined rPFS and combined PSA‐PFS. Conclusion In this study, we did not observe differences in clinical outcomes based on alternative sequencing of AA and DP in mCRPC patients. The ability to tolerate side effects and patient preference may be used to determine the treatment sequencing. In addition, high pretreatment SII level is a negative independent prognosticator of survival outcomes in mCRPC with sequential therapy using DP followed by AA or vice versa, which might guide clinicians select the best treatment.