Background According to the field effect theory, by detecting microvasculature changes such as early increase in blood supply (EIBS) in the surrounding tissue, neoplastic lesions can be identified from a distance. Objective To determine the feasibility and efficacy of a fiberoptic probe containing novel polarization gating spectroscopy technology to identify patients with pancreatic adenocarcinoma (PAC) by the field effect theory. Design Prospective cohort (pilot) study. Setting Outpatient tertiary care center. Patients Adult (≥18 years) patients undergoing EGD-EUS were screened. Patients with PAC were included in the “cancer” group and patients without PAC were included in the “control” group. We excluded patients with other known malignancies and gastroduodenal premalignant lesions. Interventions and Main Outcome Measures Spectroscopic measurements of EIBS variables, such as deoxyhemoglobin concentration (DHb) and mean blood vessel radius (BVR), were obtained from 5 periampullary locations. The Mann-Whitney rank sum test was used for the statistical analysis ( P  ≤ .05). Results Fourteen patients (mean age 72 years, 79% male) in the cancer group and 15 patients (mean age 63 years, 60% male) in the control group were included in the final analysis. At the ampullary site, both DHb ( P  = .001) and BVR ( P  = .03) were higher in PAC patients than in the control subjects. The DHb alone (92% sensitivity, 86% specificity) or in combination with BVR (92% sensitivity, 79% specificity) can differentiate PAC from control subjects with high accuracy. Limitations Small sample size, unmatched control subjects. Conclusions Spectroscopic measurements of EIBS by fiberoptic probes are feasible. Preliminary evidence suggests that in vivo measurement of normal-appearing duodenal tissue can differentiate PAC patients from a distance with high accuracy.