S2,3PSA% as a predictor of reclassification of 1st protocol biopsy on active surveillance for early-stage prostate cancer patients: From the PRIAS-JAPAN study.
Authors: Kato Takuma , Yoneyama Tohru , Hatakeyama Shingo , Tohi Yoichiro , Matsumoto Ryuji , Sato Takuma , Hashine Katsuyoshi , Kimura Takahiro , Tanikawa Toshiki , Goto Takayuki , Inoue Masaharu , Hashimoto Kohei , Ohyama Chikara , Sugimoto Mikio ,   PRIAS-JAPAN
Published: February 2025

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Background:
Recently, α2,3-sialylated prostate-specific antigen (S2,3PSA)% has been developed as a new serum biomarker for Prostate cancer (PCa). So, we aimed to investigate S2,3 PSA% to predict reclassification of the first repeat protocol biopsy (1st re-PBx) on Active surveillance (AS) for PCa patients.
Methods:
Patients who participated in PRIAS-JAPAN and its ancillary studies from August 2013 to January 2022 and met the following criteria were included: clinical stage: T1c/T2, PSA: <10ng/ml, PSA density: <0.2ng/ml/cc, number of positive cores: <2, Gleason score: <6. All participants were required to receive a blood sampling test on a protocol visit at inclusion and at the 1st re-PBx. Significant predictors of reclassification in 1st re-PBx were investigated in univariate and multivariate analyses by logistic regression analysis. Then, to assess the predictive power and thresholds for reclassification, we plotted Receiver Operating Characteristic (ROC) curves. Further, a decision curve analysis (DCA) was conducted to identify net benefits.
Results:
A total of 188 patients were analyzed. Reclassification was shown in 61 patients (32.4%). Both univariate and multivariate analysis by logistic regression analysis showed that S2,3PSA% at diagnosis and before 1st re-biopsy were both significant predictors of reclassification. In ROC analysis, S2,3 PSA% at diagnosis and before 1st re-biopsy had comparable predictive power. The AUC for S2,3PSA% before 1st re-biopsy was 0.63, with a sensitivity of 0.41 and specificity of 0.87. Analysis of the net benefit of PSA doubling time (PSADT) and S2,3PSA% with DCA using PSA, prostate volume, and age as the base model showed that S2,3PSA% had a higher net benefit than PSADT.
Conclusions:
S2,3PSA% before 1st re-PBx has a high net benefit for reclassification and is a useful tool for clinical decision making.

Result of ROC curve analysis and decision curve analysis about S2,3PSA% for reclassification at 1st repeat biopsy.

ROC curves about reclassification for differences in S2,3PSA% between baseline and before the 1st repeat PBx

Variable

AUC

Standard Error

p value
(for AUC)

95% CI

Optimal cut off point

Sensitivity

Specificity

p value
(vs baseline)

S2,3PSA%(baseline)
0.65
0.05
<0.001
0.56 - 0.74
44.3
54.1%
75.6%
-

S2,3PSA%(before 1yr PBx)
0.63
0.05
0.0065
0.54 - 0.72
1.64
41.0%
87.4%
0.33

Decision curve analysis for reclassification at 1st repeat biopsy

High Risk Threshold
0
0.1
0.2
0.3
0.4
0.5

Baseline model*
1
0.769
0.488
0.222
0.044
-0.016

Baseline model+PSADT**
1
0.77
0.492
0.29
0.011
-0.016

Baseline model+S2, 3PSA%**
1
0.769
0.504
0.215
0.186
0.131

*Baseline model is composed of age, prostate volume and PSA before 1yr PBx.

**The value of PSADT and S2,3PSA% are calculated by the data before 1yr PBx.