Head-to-head comparison of the Montreal nomogram with the detection of primary malignant circulating prostate cells to predict prostate cancer at initial biopsy in Chilean men with suspicion of prostate cancer

IntroductionThe limitations of total serum prostate-specific antigen (PSA) level values remain problematic. Nomograms may improve the predictive value of a positive prostate biopsy (PB) finding. We compare in a prospective study of Chilean men suspicious of having prostate cancer (PC), owing to an elevated total serum PSA or abnormal digital rectal examination finding or both, the use of the online Montreal nomogram for the detection of primary malignant circulating prostate cells (mCPCs) to predict a positive PB finding.Methods and patientsConsecutive men suspicious of PC underwent 12-core transrectal ultrasound PB; their age, total serum PSA levels and percent free PSA values, and Montreal nomogram scores were registered. Immediately before the PB, an 8-ml blood sample was taken to detect primary mCPCs. Mononuclear cells were obtained by differential gel centrifugation and identified using double immunomarcations with anti-PSA and anti-P504S. Biopsies were classified according to presence of cancer/no cancer. The test results for the detection of mCPC were stated as negative/positive, and the total number of cells/8 ml of blood was registered. Areas under the curve for total serum PSA level, percent free PSA value, Montreal score, and detection of mCPCs were calculated and compared. Diagnostic yields, the number of possible biopsies that could be avoided, and the number of clinically significant cancers that would be missed were calculated.ResultsOverall, 607 men underwent biopsy, where 197 (32.5%) had cancer. These men were significantly older, had higher total serum PSA level and Montreal score, and lower percent free PSA value. The values for area under the curve were 0.56 for total PSA level, 0.78 for percent free PSA, 0.78 for Montreal score, and 0.84 for mCPC detection; mCPC detection had a significantly superior prediction value (P = 0.018). Using cutoff values of percent free PSA<10%, Montreal score>50%, and≥1 mCPC detected, mCPC detection had a higher diagnostic yield. Of the 197 cancers, 41 complied with the criteria for active surveillance; percent free PSA and the Montreal score missed a higher number of significant cancers when compared with mCPC detection.ConclusionsPrimary mCPC detection outperformed the use of percent free PSA and the Montreal nomogram in predicting clinically significant PC at initial PB.