Pancreatic cancer--EUS and early diagnosis

Over the last decades, the incidence of pancreatic cancer has increased. Prognosis remains poor despite rapid improvements in imaging technologies and therapeutic modalities. Curative treatment is dependant on early diagnosis.

One of the most promising techniques for early detection of pancreatic lesions seems to be endoscopic ultrasound (EUS). With or without fine needle aspiration (FNA), it has been described as highly sensitive and accurate in staging. Superior to other imaging modalities in early studies, results in later publications declined. There are three fundamental different techniques of EUS available at present: radial scanning scopes, linear scanning scopes and radial or linear scanning probes, each with different pros and cons. Indications for EUS are persistent epigastric and/or back pain, acute onset of diabetes in the elderly, unclairified weight loss and suspect results in ultrasonography, especially in individuals over 45 years of age and in high-risk subpopulations.

In early studies, EUS was superior or at least equal to other imaging modalities regarding sensitivity, determining tumour size and extent, lymph node involvement and vascular infiltration. With rapid advances in technology, first of all, computed tomography (CT) and magnetic resonance imaging have reached better results. The highest accuracy in assessing extent of primary tumour, locoregional extension, vascular invasion, distant metastasis, tumour TNM stage and tumour resectability seems to have helical CT, whereas EUS has the highest accuracy in assessing tumour size and lymph node involvement. For assessment of tumour resectability, a combination of CT and EUS seems to be the procedure with the highest accuracy. Some new techniques promise improvement of the diagnostic yield of EUS. In differentiation to focal inflammation, contrast-enhanced EUS has shown to increase sensitivity and specificity for pancreatic cancer. Another major problem is the assessment of vascular invasion. 3D reconstructions additional to conventional EUS seemed to improve the evaluation of vessel-tumour-relationships. Endoscopic ultrasound is not a foolproof method; there are several reasons for failure, and it shows a high interobserver variety even among experienced endosonographers. Nevertheless, EUS proved to have a high negative predictive value. Poor overall survival rates and some reports of high survival rates among small resected stage 1 ductal adenocarcinomas suggest a high benefit for screening and early detection of pancreatic neoplasia, and treatment of precursor lesions might prevent their progression to invasive cancer. Because of low incidence and the lack of accurate, inexpensive and non-invasive diagnostic tests for early disease, screening for pancreatic cancer and its precursor lesions in the entire population is not reasonable. But a EUS- and CT-based screening among high-risk individuals discovered pancreatic neoplasms in eight of 78 patients, in contrast to no pancreatic neoplasia among 149 control subjects.

Screening for pancreatic cancer and its precursor lesions in the general population is not feasible, but high-risk subpopulations seem to be suitable targets for screening programs. EUS is an essential tool for diagnosis and assessment of extension and resectability of pancreatic tumours.