The current Response Evaluation Criteria in Solid Tumors (RECIST) guideline, which is based on tumor size measured by chest X-ray or CT scan, and widely used tumor markers assay (such as carcinoembryonic antigen (CEA) and neuronal specific enolase (NSE)) are not sensitive enough to monitor chemotherapy effects in an individual patient because these markers require more than a month after chemotherapy to provide the information of interest. Here, CEACAM5 is linked to neoplasm.