Pancreatic ductal adenocarcinoma : computed tomography for diagnosis, local staging and prediction of postoperative complications
Sammanfattning: Pancreatic ductal adenocarcinoma (PDAC) is a disease with a dismal prognosis, being the 4th leading cause of cancer deaths in Sweden and worldwide. The only potentially curative therapy is surgery. Unfortunately, by the time of diagnosis only 20% of patients have a resectable tumor and the overall 5-year survival rate does not exceed 5%. One of the main reasons for this is that some tumors are not detected, either because of small size or difficulty in delineation. Another reason is the underestimation or in some cases overestimation of the local tumor staging. These patients undergo an extensive but unnecessary operation or are withheld from potentially curative surgery, respectively. In some cases the patients develop serious postoperative complications, which can be predicted and perhaps avoided with proper preoperative planning. Technological advances in multidetector computed tomography (MDCT), combined with its wide availability, have made MDCT the modality of choice for PDAC imaging. The overall purpose of this thesis was to investigate the role of MDCT in patients with PDAC in terms of (i) tumor diagnosis, (ii) local staging assessment and (iii) prediction of postoperative complications. In Study I, we compared low-tube-voltage (80 kV) with normal-tube-voltage (120 kV) protocols regarding tumor detection by using a phantom that simulated the normal pancreatic parenchyma and hypovascular tumors. Our results showed that low tube-voltage significantly improves tumor detection. In Study II, we evaluated 30 MDCT examinations of the pancreas in patients with PDAC in the pancreatic head, obtained according to our institution’s standard protocol (120 kV and 0.75 g iodine (I)/kg body-weight). Based on our hospital’s classification system, we investigated the interobserver agreement among radiologists in local tumor staging assessment and the correlation of this assessment to the surgical outcome. Our results showed almost perfect agreement among radiologists as well as an increased risk for vascular involvement with more advanced preoperative staging. In Study III, we compared low-tube-voltage normal-iodine-load (80 kV and 0.75gI) with low-tube-voltage high-iodine-load (80 kV and 1gI) and with normal-tube-voltage normaliodine- load (120 kV and 0.75gI) protocols in 30 patients with PDAC, regarding tumor conspicuity and local vessel involvement. Our results showed that low tube-voltage and high iodine-load significantly improve tumor conspicuity. In Study IV, we correlated the pancreatic remnant volume (PRV) and pancreatic duct width (PDW) in 182 patients undergoing pancreaticoduodenectomy (PDE), to the risk for pancreatic leakage and fistula (PF) formation. Our results showed a significantly higher risk for PF in patients with high PRV and/or small PDW. In conclusion, a high-quality preoperative MDCT is a very useful tool in the evaluation of PDAC in terms of tumor diagnosis, staging and prediction of postoperative complications. The low-tube-voltage high-iodine-load technique has the potential to improve tumor diagnosis and local staging.
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