TABLE 51 Detection of Pancreatic Carcinoma by Body Imaging Tools

Size EUS US CT ERCP AG

> 20 mm (N = 136) 135/136 104/132 102/136 121/136 77/80

Total sensitivity (%) 143/146 (98) 107/142 (75) 103/129 (80) 128/146 (86) 80/90 (89)

AG = angiogram; CT = computed tomography; ERCP = endoscopic retrograde cholangiopancreatography; EUS = endoscopic ultrasonography; US = ultrasonography.

underwent EUS with or without FNA as part of their pancreatic cancer evaluation. Surgery and further diagnostic testing were avoided in 41% and 57% of patients respectively. A substantial cost saving of $3,300 per patient was calculated. In a series of 216 consecutive patients, the use of EUS with EUS-guided FNA as the initial approach to patients with obstructive jaundice was studied by Erickson and colleagues. EUS/FNA proved useful not only as a diagnostic and staging modality, but also served in directing the need for subsequent therapeutic ERCP, saving approximately $1,007 to $1,313 per patient.In addition,if EUS/EUS-guided FNA were not used at all, an extra $2,200 would be spent per patient. The economic impact of EUS-FNA in the preoperative staging of patients with pancreatic head AC was clearly demonstrated in a decision analysis model by Harewood and colleagues (2002). The use of EUS-FNA prevented 16 surgeries per 100 patients compared with 8 per 100 patients if CT-guided FNA was performed for nonperitumoral lymph nodes (NPT LN). If the frequency of NPT LN was > 4%, then EUS-FNA is the least costly procedure ($15,938) versus ($16,378) for CT-FNA, and ($18,723) for surgery. EUS-guided FNA of the pancreas, unlike CT-guided FNA, can be preformed during the initial endosonographic procedure. The overall complication rate of EUS-FNA was reported to be 0.5 to 2.9%. Several case reports had described malignant seeding of the needle tract after transcutaneous FNA. The true incident has yet to be established. Theoretically, EUS-guided FNA of pancreatic cancers should have lower chance of malignant seeding because of the short needle tract. In pancreatic head lesions, EUS-guided FNA is usually performed from the second portion of the duodenum, a segment resected surgically along with the tumor during Whipple procedure. This is another theoretical advantage in eliminating the needle tract and decreasing the risk of malignant seeding when compared with the percutaneous approach. However, this may not apply to pancreatic body and tail lesions, where the possibility of malignant seeding of the gastric wall could still exist. The ability to detect vascular structures around the targeted lesion by Doppler flow analysis is another advantage as to minimize the bleeding complication rate. Most of the bleeding is self-limited and resolves spontaneously.

EUS Staging

The initial studies on the staging accuracy of EUS for pancreatic cancer were very encouraging. These results showed that EUS had a T-stage accuracy of 85 to 94% and a N-stage accuracy of 72 to 80%. During this time period, EUS T-stage and N-stage accuracy was superior to conventional imaging with either transabdominal US or CT. Thus, in the early 1990s, it was stated that "EUS is the single best modality for the preoperative local staging of pancreatic cancer." However, over the last 5 years, this notion has been challenged. The controversies that have arisen include the following: (1) more recent studies do not confirm the earlier staging accuracies of EUS compared to findings at surgery and (2) EUS is not thought to be useful for metastatic (M) staging, and therefore is restricted to local staging. Therefore, a helical CT is still necessary. As helical CT and magnetic resonance imaging (MRI) studies are improving for local staging, is there still a role for EUS in the staging of pancreatic cancer? In other words, in the year 2004, is CT alone sufficient in staging pancreatic cancer? The T-stage accuracy for EUS in the recent literature (1999 to present) ranges from 69 to 85%. Taking the combined accuracy of these studies, the mean accuracy for EUS T-stage accuracy is 77% (95% CI 70 to 83%) (Table 5-2). The N-stage accuracy ranges from 54 to 72%. The calculated combined nodal accuracy is 69% (95% CI 56 to 71%, Table 5-3).

EUS versus Helical CT

Although the gap is closing between EUS and CT in staging pancreatic cancer, EUS/FNA still remains in many ways

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