Optimal sequential therapy for metastatic castration-resistant prostate cancer after androgen receptor pathway inhibitors in the up-front era.

Abstract

168 Background: The optimal sequential therapy for metastatic castration-resistant prostate cancer (mCRPC) following the use of up-front androgen receptor pathway inhibitors (ARPIs) for metastatic hormone-sensitive prostate cancer (mHSPC) is still unclear. Methods: A total of 220 patients who received systemic therapy for de novo mHSPC at Nagoya University Hospital and its affiliated institutions between 2014 and 2022 were included in the study. Patients who received up-front therapy with ARPI as first-line therapy for mHSPC, followed by ARPI as primary therapy for mCRPC were defined as the AA group, followed by docetaxel (DOC) as primary therapy for mCRPC were defined as the AD group. On the other hand, the vAA group was defined as patients who received androgen deprivation therapy alone or combined androgen blockade as “vintage” first-line therapy for mHSPC, followed by two consecutive ARPIs as sequential therapy for mCRPC, and the vAD group was defined as patients who received ARPI followed by DOC as sequential therapy for mCRPC. Patient characteristics and progression-free survival (PFS) of the second agent after the first ARPI were compared in each group. Results: We identified 14 patients in the AA group, 16 in the AD group, 84 in the vAA group, and 59 in the vAD group. There were no differences in patient background such as initial PSA, Gleason score, and metastatic burden between the groups, while patient age was lower in the AD and vAD groups compared to the AA and vAA groups. The PFS of the second agent in the AA group was significantly shorter than that in the vAA group (median, 6.8 vs. 1.9 months; hazard ratio [HR], 0.25; 95% confidence interval [CI], 0.25-0.87; p=0.017). In contrast, there was no significant difference in PFS of the second agent in the vAD and AD groups (median, 7.0 vs. 4.0 months; HR, 0.63; 95%CI, 0.29-1.34; p=0.235). Conclusions: The effect of each agent after ARPI therapy in the UP-FRONT era may be poorer than that in the VINTAGE era. In the setting after up-front ARPI, sequential therapy with DOC may be more appropriate than sequential therapy with ARPI.