Predicting malignancy in pre-neoplastic lesions detected during screening for pancreatic cancer

Abstract

Background: Screening is offered to individuals who have an identified increased risk of pancreatic cancer. Such risks may be increased because of a family history or a known genetic mutation which has been shown to confer increased risk. Amongst those being screened intraductal papillary mucinous neoplasm (IPMN) of the pancreas are increasingly common entities being detected incidentally; their risk of malignancy can be as high as 85%. Consensus guidelines exist for the management of these lesions – the morbidity associated with pancreas resection is as high as 50%. We set out to identify a marker which could be used to identify those IPMN which should be resected and those which may be safely observed. Methods: Individuals were identified from the European Registry of Hereditary Pancreatitis and Familial Pancreatic Cancer (EUROPAC) or patients identified in Liverpool or Hedielberg with cystic lesions and/or pancreatic cancer. Cancer screening was performed by imaging and with molecular analysis (including mutation analysis of TP53) of pancreatic juice obtained by endoscopic retrograde cholangiopancreatography (ERCP). Matched tissue sections and frozen sections of pancreatic tissue from 73 patients who underwent resection for IPMN were assessed histologically and for mutations in TP53 status using a novel limiting dilution Next Generation Sequencing technique. Results were assessed relative to clinical outcomes. Results: Amongst those 29 individuals who were screened with ERCP, 11 had IPMN, 7 IPMN with cancer (IPMC) and 3 pancreatic ductal adenocarcinoma (PDAC). The remaining cases were benign neoplastic or inflammatory conditions. Kaplan-Meier survival analysis at 5 years found that the presence of p53 mutation in the tissue was a better prognostic marker of survival than the histological diagnosis alone (p=0.0152 vs. p=0.0819). Sensitivity and specificity of p53 mutation as a predictor of survival was calculated as 0.89 and 0.95 respectively. There was 100% correlation between the p53 mutational status of the resected tissue and the pancreatic juice obtained at ERCP. When ERCP was assessed as a method for screening, however, there was found to be an unacceptably high incidence of post-ERCP pancreatitis (PEP) 7 cases of PEP in 16 ERCPs (44%). This rate was shown to be significantly reduced to 15% (6/40) with the use of pancreatic stent and diclofenac, but the overall prevalence of PEP was 23.2% over 14 years. There were no cases of PEP amongst those individuals being screened because of hereditary pancreatitis. Of 27 IPMN cases with frozen tissue 23 individuals had TP53 mutations. Seven cases died of pancreatic cancer after resection. Kaplan-Meier survival analysis revealed that one mutation p.L264R predicted survival regardless of histology (p=<0.0001). The mutation was present in 6 of the 7 cases who died and in none of those who survived to 5 years. Mutation specific PCR was used to validate results showing that p.L264R discriminated between survivors and IPMN cases who died of cancer (AUC = 0.79). Conclusions: IPMN continues to cause concern and uncertainty among those individuals being screened for cancer who are largely well and asymptomatic. The p.L264R mutation could be used to differentiate those IPMN which result in poor survival to facilitate potentially curative surgery. The mutation may be present in pancreatic juice which can be collected endoscopically as a screening tool. The use of prophylactic measures to reduce PEP may be considered sufficient to bring the risk of complications to an acceptable level when compared to the relative certainty of prognosis afforded by a positive test for p.L264R.