Changes in Tumor Vascularity Depicted by Contrast-Enhanced Endoscopic Ultrasonography as a Predictor of Treatment Efficacy in Patients With Locally Advanced and Metastatic Pancreatic Cancer (PEACE)

Introduction and rationale:

Pancreatic cancer (PC) is one of the most lethal and therapeutically resistant malignancies, with a grim prognosis that is attributed to the late clinical presentation and the relative chemoresistance of the disease.

Even with identical chemotherapy regimens, some patients experience improvements in survival and tumor response, whereas other patients only experience inconvenience and increased toxicity. It has been suggested that the burden of treatment should not be added to the suffering of those with advanced pancreatic cancer. Therefore, understanding prognostic factors before treating patients with antitumoral agents may be helpful in selecting those patients predicted to have an improved survival and tumor response after treatment.

Studies have shown that angiogenesis is an important factor that influences the prognostic of solid tumors, including pancreatic tumors. Contrast-enhanced imaging methods can offer detailed information on tumor vascularity. Contrast-enhanced endoscopic ultrasound (CE-EUS) is a new method which allows detailed characterization of focal pancreatic masses. CE-EUS offers high-resolution images of the pancreas that far surpass those achieved by computed tomography, ultrasound, or magnetic resonance imaging. CE-EUS can detect intratumoral vessels in the pancreatic lesions. One of the fluoro-gas-containing contrast agents used in CE-EUS is Sonovue®, which is isotonic, stable and resistant to pressure, with a viscosity similar to blood. It does not diffuse into the extravascular compartment remaining within the blood vessels until the gas dissolves and is eliminated in the expired air (blood pool contrast agent). The safety profile of SonoVue showed a very low incidence of side effects; it is not nephrotoxic and the incidence of severe hypersensitivity is similar to other magnetic resonance imaging contrast agents. Moreover, Sono-Vue is approved for clinical use in European Union countries.

The hypothesis that tumors with intratumoral vessels are chemosensitive appears to be reasonable because drugs penetrate tumors through vessels. Therefore, it is possible that hypoxic condition in tumor tissue leads to chemoresistance and poor prognosis in patients with pancreatic carcinoma who received systemic chemotherapy. However, whether low vascularized tumors correlate with the chemoresistance and poor prognosis is still unclear. Patients with non-resectable pancreatic cancer have an especially poor prognosis and have many severe symptoms.The analysis of prognostic factors before treatment may be helpful in selecting appropriate candidates for chemotherapy and determining treatment strategies. For example, patients who have a poor prognosis may be treated best with only supportive care because of their short survival. Consequently, the aim of the PEACE study is to assess the vascularity of pancreatic malignant tumors with CE-EUS and to clarify the prognostic value of tumor vascularity in patients with advanced PC.