Most (> 90%) pancreatic adenocarcinomas harbour mutations in codon 12 of the K-ras gene . Many studies have reported detection of the oncogene in material obtained during endoscopic retrograde cholangiopancreatography (ERCP) in patients with pancreatic cancer. K-ras mutations have been detected in bile , pancreatic juice , pancreatic brushings , and duodenal aspirates . This approach to diagnosis of pancreatic cancer is attractive, as tissue diagnosis is otherwise difficult and invasive. In our region, for example, a formal tissue diagnosis is established in only one-third of patients with pancreatic cancer .
The sensitivity of molecular diagnosis on material obtained at ERCP varies enormously. We detected K-ras mutations in bile in 50% of patients with pancreatic cancer ; van Laethem et al.  reported a prevalence of 83% in pancreatic brushings; and in this issue of the European Journal of Gastroenterology and Hepatology, Boadas et al.  detected the mutation in secretin-stimulated pancreatic juice in 44% of pancreatic cancer patients. We used bile because it was easy to collect following biliary stenting, and because collection did not add significantly to procedure duration. Collection of pancreatic juice following secretin stimulation probably takes a little longer, whilst carrying out pancreatic brushings is likely to double the duration of the procedure. In our experience in the UK, when patients with pancreatic cancer come for ERCP, the primary objective is to establish biliary drainage by stent insertion. In our series, less than 50% of patients with pancreatic cancer had a pancreatogram, as most endoscopists would proceed to stent insertion if the bile duct is cannulated first. The Belgian group  carry out ERCP under general anaesthesia, which allows for a more leisurely approach, and is likely to facilitate procedures such as pancreatic duct brushings.
Initial enthusiasm for molecular diagnosis on material obtained at ERCP has been tempered by the detection of K-ras mutations in patients with chronic pancreatitis. Pancreatic cancer may be difficult to distinguish from chronic pancreatitis, as chronic pancreatitis is associated with both ductal and parenchymal changes that can mimic pancreatic cancer. As chronic pancreatitis is therefore the main differential diagnosis in patients with suspected pancreatic cancer, detection of K-ras mutations is unlikely to play a significant role as a diagnostic marker of pancreatic cancer. Furthermore, the evidence that presence of the mutation identifies those patients with chronic pancreatitis who are at particular risk of developing pancreatic cancer is conflicting. Boadas et al. diagnosed pancreatic cancer in one patient with chronic pancreatitis and K-ras, but this diagnosis was established after only 1 month of follow-up. Furthermore, another chronic pancreatitis patient without the mutation went on to develop pancreatic cancer.
Cytology (biliary and pancreatic, aspiration and brushings) has proved disappointing in the diagnosis of pancreatic cancer. Boadas et al. reported positive cytology in only 27% of pancreatic cancer patients. The combination of cytology and K-ras increased the ‘diagnostic’ rate to 50%. Although cytology has a poor sensitivity, it has a high specificity, and will therefore continue to play a role in the clinical diagnosis of pancreatic cancer. Although cytology was positive in only 27% of this series, other groups have reported much higher sensitivities, particularly when pancreatic brushings are used .
This study raises a number of questions: (1) does the presence of K-ras in material obtained at ERCP have a role to play in diagnosis of pancreatic cancer or clinical decision making? Boadas et al. concluded that ‘when a K-ras mutation is present in pancreatic juice, in patients without chronic pancreatitis, pancreatic cancer is highly suspected.’ We would concur with this conclusion, with the caveat that the most likely alternative diagnosis in patients with suspected pancreatic cancer is chronic pancreatitis. (2) Are patients with chronic pancreatitis and K-ras at higher risk of developing pancreatic cancer than chronic pancreatitis patients without K-ras? Van Laethem  and Barthelemy et al.  followed up patients with chronic pancreatitis and K-ras, and both studies detected two cancers over the follow-up period. By contrast, a Japanese study  of 54 patients detected no cancers in 20 patients over a mean follow-up period of 78 months. (3) How should we manage patients with chronic pancreatitis in whom K-ras mutations have been detected? The approach of Boadas et al. seems sensible and pragmatic, although there is little evidence as yet that such an approach is likely to detect early cancer. Should these patients undergo regular surveillance with ERCP and brush/aspiration cytology? Van Laethem  has commented that only long-term prospective studies will answer this question, and such a study has been initiated by the Brussels group. The significance of K-ras in chronic pancreatitis has not, therefore, been defined clearly, and detection of the mutation may lead to anxiety for both patient and clinician, without clear consensus on follow-up and treatment.
The presence of K-ras mutations in pancreatic juice (and other material obtained at ERCP) is not specific enough to justify its use in clinical practice. Other tumour markers, such as p53  and telomerase  may, in combination with K-ras, increase the specificity, but further studies are required to define the role of combinations of tumour markers in the diagnosis of pancreatic cancer.
We conclude that K-ras is biologically significant but, at present, not clinically useful in the diagnosis of pancreatic cancer.
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