Evaluation of computed tomography for lymph node staging in bladder cancer prior to radical cystectomy

Objectives: To retrospectively evaluate the value of CT for lymph node (LN) staging in bladder cancer. Methods: Two uroradiologists reviewed CT scans of 231 patients who underwent radical cystectomy and pelvic lymphadenectomy according to a predefined 12-field template. A 5-step model was used to grade the radiological likelihood of a LN to represent malignant spread based on size, configuration and structure as well as regional clustering. Statistical analyses were performed both on patient-and field-based levels. Results: LN metastases were found in 59 of 231 patients (25.5%). On a patient-based level, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy were 52.6, 93.6, 73.2, 85.6 and 83.4%, respectively. Using the field-based approach, a total of 1,649 anatomical fields were evaluable, of which 114 fields showed malignancy (6.9%). On a field basis, sensitivity, specificity, PPV, NPV and accuracy were 30.2, 98, 51.5, 94.5 and 93.3%, respective-ly. Concerning local staging (pT category), the overall accuracy was 78%; overstaging occurred in 6% and understaging in 16%. Conclusions: In line with prior studies, the sensitivity of CT imaging for the detection of LN metastases was low, while high values for specificity were achieved. This was further underlined by analyzing standardized anatomical fields. Concerning local staging, postoperative changes after TURBT rarely led to overstaging.