Although
gemcitabine monotherapy is the standard treatment for advanced
pancreatic cancer, patient outcome varies significantly, and a considerable number do not benefit adequately. We therefore searched for new
biomarkers predictive of overall patient survival. Using LC-MS, we compared the base-line plasma
proteome between 29 representative patients with advanced
pancreatic cancer who died within 100 days and 31 patients who survived for more than 400 days after receiving at least two cycles of the same
gemcitabine monotherapy. Identified
biomarker candidates were then challenged in a larger cohort of 304 patients treated with the same protocol using reverse-phase
protein microarray. Among a total of 45,277
peptide peaks, we identified 637 peaks whose intensities differed significantly between the two groups (p < 0.001, Welch's t test). Two MS peaks with the highest statistical significance (p = 2.6 x 10(-4) and p = 5.0 x 10(-4)) were revealed to be derived from alpha(1)-antitrypsin and
alpha(1)-antichymotrypsin, respectively. The levels of alpha(1)-antitrypsin (p = 8.9 x 10(-8)) and
alpha(1)-antichymotrypsin (p = 0.001) were significantly correlated with the overall survival of the 304 patients. We selected alpha(1)-antitrypsin (p = 0.0001), leukocyte count (p = 0.066),
alkaline phosphatase (p = 8.3 x 10(-8)), and performance status (p = 0.003) using multivariate Cox regression analysis and constructed a scoring system (nomogram) that was able to identify a group of high risk patients having a short median survival time of 150 days (95% confidence interval, 123-187 days; p = 2.0 x 10(-15), log rank test). The accuracy of this model for prognostication was internally validated and showed good calibration and discrimination with a bootstrap-corrected concordance index of 0.672. In conclusion, an increased level of alpha(1)-antitrypsin is a
biomarker that predicts short overall survival of patients with advanced
pancreatic cancer receiving
gemcitabine monotherapy. Although an external validation study will be necessary, the current model may be useful for identifying patients unsuitable for the standardized
therapy.