Biology and usefulness of [-2]proPSA as a prognostic marker in CRPC patients.

Abstract

242 Background: Prostate health index (phi) using -2proPSA (p2PSA), which is a precursor of PSA, has been reported to be useful as a marker for predicting the presence of cancer in the gray zone with a PSA value of 4-10 ng/ml. There is no detailed report on the biology of p2PSA in castration resistant prostate cancer (CRPC) patients and it is unknown. We retrospectively investigated the biology of p2PSA and its usefulness as a marker using CRPC patient's samples. Methods: The study was performed using samples from a prospective study of CRPC patients treated with enzalutamide. We examined 98 pre-enzalutamide treatment serum samples that can measure p2PSA. The samples were collectively measured by Beckman Coulter (Tokyo, Japan). We also examined the correlation between the measurement results of p2PSA and the prognosis of phi and CRPC patients calculated accordingly. This study was approved by the IRB of Gunma University Hospital (IRB 2021-092, 1983). Results: The study population of 98 patients had a median age of 73 years. The median PSA before administration of enzalutamide was 23.8 ng/ml, the median p2PSA was 208.8 pg/ml, and the median phi was 188.0. The median values of each parameter were divided into two groups, and the PSA progression free survival (PSA-PFS) and overall survival (OS) rate were compared by the Kaplan-Meier method. In the study of PSA-PFS, PSA, p2PSA, and phi could not be significant markers. In the OS study, the median OS of the PSA low group was NYR (not yet reached), the high group was 26.8 months, the p2PSA low group was NYR, the high group was 26.8 months, the phi low group was NYR, and the high group was 26.8 months. The OS was significantly better in the low- value group for each parameter (p-values 0.024, 0.034, 0.018, respectively). Conclusions: The biology of p2PSA in CRPC patients has been clarified. Although we couldn't find a clear advantage over PSA, we would like to add a study based on the data of this study.