The prognostic role of IDC-P in mCRPC and its predictive value in those treated with docetaxel or abiraterone as first-line therapy.

Abstract

e603 Background: Intraductal carcinoma of prostate (IDC-P) is recognized as a newly pathological entity in 2016. Its role in metastatic castration-resistant prostate cancer (mCRPC) remains unknown. The aim of this study is to explore the association of IDC-P with clinical outcomes and to further identify its potential predictive role in making first-line treatment decision for mCRPC patients. Methods: We retrospectively analyzed data of 131 men with mCRPC. IDC-P was diagnosed by re-biopsy at the time of mCRPC. After mCRPC, 45 and 41 patients received abiraterone (Abi) or docetaxel (Doc) as first-line therapy, respectively. PSA response, PSA progression-free survival (PSA-PFS) and overall survival (OS) from mCRPC to death were analyzed. Kaplan-Meier curves, log-rank test, Cox regression models and Harrell’s C-index were conducted to analyze disease progression, treatment efficacy and outcomes. Results: The incidence of IDC-P in mCRPC reached to 47.3%. IDC-P was not only related to rapid PSA progression, but also associated with 20-month decrease of OS. Among IDC-P(-) patients, PSA response, PSA-PFS and OS were comparable in Abi-treated and Doc-treated groups. In contrast, among IDC-P(+) patients, PSA response rate is higher in Abi-treated vs. Doc-treated group (52.4% vs. 21.7%; p = 0.035), also, PSA-PFS and OS were much longer in Abi-treated group (PSA-PFS:13.5 vs.6.0 months, p = 0.012; OS:23.6 vs.14.7 months, p = 0.128). Cox regression indicated that, for IDC-P(+) patients, Abi was associated with prolonged time of PSA-PFS (HR = 0.33, 95%CI: 0.14-0.79, p = 0.013), and could significantly increase the predictive accuracy of standard model, with an obvious increase of the C-index from 0.719 to 0.778 (p = 0.009). Conclusions: The presence of IDC-P in mCRPC from re-biopsy was not only an independent prognosticator for clinical outcomes, but also strongly associated with poor response to Doc-based chemotherapy. We also found that IDC-P status could be considered as a novel predictive marker in helping physicians precluding Doc as first-line therapy in IDC-P(+) patients. Also, these findings require large-scale prospective validation.