Development of a nomogram for predicting the risk of positive prostate biopsy

Abstract

Objective We develop a nomogram for predicting the risk of positive prostate biopsy based on clinic indexes of patients. Methods We retrospectively analyzed the clinical data of patients who underwent prostate biopsy for prostate cancer in our hospital from July 2009 to March 2015. Variables including age, prostate volume, free PSA (fPSA) and total PSA (tPSA) were collected. 958 patients with integrity data, which PSA was under 100 ng/ml, were enrolled in this study. Of these patients, we randomly selected 20% as validation group (191), and the other 80% as development group (767). We performed Logistic regression analysis to identify the independent risk factors related to positive prostate biopsy in development group. Then we constructed a prediction model according to regression equation to predict the result of prostate biopsy. Receiver operating characteristic (ROC) analysis was performed to verify the diagnostic value of the novel prediction model, which was furtherly compared with the diagnostic values of PSA alone, f/t PSA, PSAD respectively. Result The age of benign prostatic hyperplasia was (67.3±9.7)years, tPSA (12.4±8.8)ng/ml, the prostate volume (69.2±50.6)cm3. The age of prostate cancer was(71.6±9.7)years, tPSA (24.3±21.3)ng/ml, the prostate volume was (46.0±34.0)cm3. The fPSA, tPSA, PSAD, f/tPSA, age and prostate volume were independent risk factors by Logistic regression analysis, the ORs were 1.094, 1.551, 0.958, 0, 13.647 and 0.985 respectively(P<0.05). The nomogram based on all variables was established. The area under the ROC curve of the model (0.854) was greater than those of tPSA (0.709), f/tPSA (0.667) and PSAD (0.807) (P<0.05). Conclusions The nomogram established in this study has better diagnostic value for prostate cancer compared with PSA and other PSA related parameters, which is a simple and convenient method without additional medical spending. Key words: Prostate Cancer; Models, Statistical; Prostate-Specific Antigen(PSA)