A Nomogram Predicting Lymph Node Metastasis in Patients with Prostate Cancer Undergoing Ultrasound-Guided Transrectal Prostate Biopsy

Ultrasound-guided transrectal prostate biopsy was widely used to diagnose prostate cancer. The prediction of lymph node metastases was not yet explored in prostate cancer undergoing ultrasound-guided transrectal prostate biopsy. We analyzed the clinical data from 235 prostate cancer patients, and 134 patients met the criteria and were included for analysis. To identify independent risk factors for lymph node invasion, univariate and multivariate logistic regression analyses were performed. A nomogram predicting lymph node metastasis was developed and validated by R software. Patients received an average of 12.8 prostate biopsies. A mean of 8.25 positive biopsy indicated prostate cancer. The mean Gleason score was 7.25. We found that 37 of 134 patients had lymph node invasion; the mean number of positive lymph node was 2.63. Three models (named LN4, LN5, and LN7) were developed using different variables. Multivariate logistic analyses were performed and area under the curve values were calculated. LN5 built based on five predictive variables (positive biopsy in external and internal glands, percentage of positive biopsy, and primary and secondary Gleason grades) showed good calibration, with an area under the curve value of 88.2%. Our nomogram could predict lymph node invasion in prostate cancer patients diagnosed via ultrasound-guided transrectal prostate biopsy. It also contributed to selecting good candidates for surgery with lymph node dissection.