Population-based validation of the National Comprehensive Cancer Networkrecommendations for baseline imaging for bladder cancer: a case for routine baseline bone scan?

Abstract

This study aims at evaluating the performance of some of the imaging recommendations of the National Comprehensive Cancer Network (NCCN) for initial evaluation of bladder cancer. Surveillance, epidemiology and end results program (2010-2015) was queried and patients with clinically (T1-T4) bladder cancer and complete information about clinical T/N (tumor/nodal) stage and metastatic sites were extracted. The following characteristics were evaluated in the current analysis: sensitivity,specificity, number needed to investigate (NNI), positive predictive value (PPV), negative predictive value and accuracy. According to the current NCCN guidelines, PPV (for the recognition of lung metastases) is 4.7% and NNI to detect one case of lung metastasis is 21.2. Similarly, PPV (for the recognition of liver metastases) is 3.1% and NNI to detect one case of liver metastasis is 32.2. Using a different imaging threshold (i.e., routinely imaging all patients >T2N0), PPV (for the recognition of lung metastases) is 10.4% and NNI to detect one case of lung metastasis is 9.6. Similarly, PPV (for the recognition of liver metastases) is 7% and NNI to detect one case of liver metastasis is 14.2. The above two thresholds were also evaluated for routine bone scanning. PPV (for the detection of one case of bone metastasis) is 5.3% using the first threshold and 11.2% using the second threshold. Imaging per current NCCN guidelines results in few patients with undetected asymptomatic lung or liver metastases. A routine baseline bone scan should be additionally considered for some asymptomatic patients with muscle-invasive disease.