Activated leukocyte cell adhesion molecule (ALCAM) was identified as a significant marker for circulating tumor cells (CTCs) with low epithelial cell adhesion molecule (EpCAM) expression in pancreatic ductal adenocarcinoma as well as brain metastases of non-small cell lung cancer and validated as a novel alternative surface marker on EpCAM-low CTCs. This evidence concerns the gene EPCAM and pancreatic ductal adenocarcinoma.