Diagnostic value of ProGRP for small cell lung cancer in different stages

To investigate the roles of gastrin-releasing peptide (ProGRP) in the diagnosis of small cell lung cancer (SCLC).

We retrospectively analyzed data from 11,206 patients with clinical suspicion of lung cancer from January 1, 2015 to May 31, 2018. ProGRP and neuron-specific enolase (NSE) were detected in peripheral blood, and receiver operating characteristic curve (ROC) was used for analysis.

ROC indicated that the cutoff values of ProGRP and NSE were 66 ng/L and 18 µg/L respectively, and the diagnosis efficacy of ProGRP was greater than that of NSE (sensitivity: 86.5% vs. 78.8%; specificity: 96.5% vs. 86.3%, respectively) in the diagnosis of SCLC. Moreover, the median level of ProGRP in SCLC increased with the accompanying stages (P<0.001). Further analysis showed that diagnostic efficacy can be improved by using different cutoff values in different stages, but not stage I and II. The cut-off values of ProGRP in the diagnosis of SCLC in stage I-II, III and IV were 56, 71 and 99 ng/L respectively. In addition, the sensitivity (96.6% vs. 95.8% and 98.3% vs. 94.8%) and concordance rate (χ² =1,526.9 and 988.7, both P<0.001) of detecting SCLC was improved by using different cutoff values compared with the only criteria of ProGRP being ≥66 ng/L in stage III and IV, but not stage I-II. Additionally in stage III and IV, the concordance rates of ProGRP ≥71 ng/L and ProGRP ≥99 ng/L were also higher than ProGRP ≥300 ng/L (both P<0.001), which was conventionally indicated for SCLC.

ProGRP has significantly higher sensitivity and specificity than NSE in the diagnosis of SCLC. Furthermore, special thresholds for every stage may be more reasonable for the diagnosis of SCLC.