Determination of critical cut-off values of PCA3 index in patients with prostate gland pathology

Abstract

Introduction. Prostate cancer antigen-3 (PCA3) is a genetic biomarker, which got widespread and demonstrated high diagnostic potential. This gene expresses only in prostate gland tissue, furthermore, malignant prostate neoplastic transformation leads to 70 – 100 time overexpression of it. Polyadenylated matrix RNA (mRNA) is a functional product of this gene, which do not translating into protein. Gene contains of four introns and three exon. Product of PCA’s gene detecting in post massage urine using polymerase chain reaction (PCR) in combination with reverse transcription. It could use as prognostic biomarker in patients with first negative biopsy or before it performing. Moreover, index of PCA3 can be useful in detecting tumor aggressiveness and decisions about further treatment options. Taking into account these facts, patients with high initial PSA level can avoid unnecessary biopsies. Objective: to determine critical cut-off value of PCA3 index as prognostic biomarker of PCa development. Materials and methods. Research based on routine and special test’s data of 243 men in Institute of Urology, National Academy of Medical Sciences of Ukraine in period of 2015–2020 year. RNA extraction from postmassage urine samples performed using RNeasy (Qiagen) kit. Statistical analysis performed using SPSS Statistics 19.0 (IBM SPSS Statistics 19.0) та SAS 12.0 (IBM Statistical Analysis System 12.0). Critical cut-off values determined using three methods: calculating of average value and (Xave) and standard deviation (SD) of it, Heiner index, and Youden’s index. Evaluation of optimality of determined critical cut-off values performed by comparative analysis using index of positive prognosis (IPP), index of negative prognosis (INP), diagnostic accuracy of method (DAM), Sp and Se for each of used methods. Results and discussion. First method demonstrated than 97,5 % of all results, which means absent of disease, was below critical cut-off values, due to statistical deviations and accurate demonstrate than in case of asymmetry or multimodal distribution this method was unsatisfied. Wherein IPP was 95 %, INP – 72 %, DAM – 78 %, Sp – 97,5 % and Se – 52 %. Calculation of PCA3 index area under ROC-curve was 0,810 (0,771–0,849). Using Heiner’s method critical cut-off value of PCA3 index was 14,0 с. u., where in IPP was 75 %, INP – 82 %, DAM – 78 %, Sp – 78 % and Se – 78 %. Critical cut-off values of PCA3 index 33,4 c. u. which calculated by Youden’s index demonstrated IPP – 98 %, INP – 73 %, DAM – 80 %, Sp – 99 % and Se – 57 %. Conclusions. The most optimal critical cut-off value for PCA3 index was determined using Youden’s index and was 33,4 c. u. Keywords: prostate cancer, PCA , prostate cancer antigen-3, PCA3, prostate cancer antigen-3 index, PCA3 index, critical cut-off values of PCA3 index.