Patients with unresectable pancreatic cancer have a poor prognosis. The analysis of prognostic factors before treatment may be helpful in determining the best therapeutic strategies. The aim of the PEACE study is to assess the vascularity of pancreatic malignant tumors using contrast-enhanced harmonic EUS (CEH-EUS) and to clarify the prognostic value of tumor vascularity in patients with locally advanced and metastatic pancreatic cancer. Hereby, we present the protocol of a prospective, nonrandomized, single-arm, multicenter study aiming to assess changes in tumor vascularity using CEH-EUS before and 2 months after treatment initiation in patients with unresectable, locally advanced/metastatic pancreatic cancer and to examine the correlation between vascular changes and treatment response, progression-free survival, and overall survival.