Small pancreaticobiliary tumors, such as PC and BC, are difficult to diagnose because they have minimal symptoms in the early stages. However, advanced pancreaticobiliary cancers exhibit a poor prognosis. The 5-year survival rate of PC patients is approximately 8%, and PC is the fourth leading cause of cancer death worldwide [12, 13]. The early diagnosis of PC is one solution to improving the prognosis of PC, and various approaches have been developed such as genetic screening of high-risk patients [14, 15].
EUS is considered to be a sensitive device for the diagnosis of pancreaticobiliary diseases [16-18]. In particular, curved linear array EUS can obtain tissue by EUS-guided fine needle aspiration (EUS-FNA), and has become the scope that is predominantly used for EUS examination. Meanwhile, radial scan EUS is used for screening examinations, and can obtain transverse images of the pancreas, which provides objective evaluations. However, these scopes are dedicated EUS devices, and are unsuitable for medical check-ups.
On the other hand, EGD using a forward-viewing endoscope and transabdominal ultrasound are commonly used in medical check-ups in Japan [19]. A forward-viewing radial scan ultrasonic endoscope and ultrasound processor (SU-1 and EG-580UR, respectively; FUJIFILM, Tokyo, Japan) enable single-session screening of the upper gastrointestinal tract and pancreaticobiliary organ. EUS provides high-resolution images, and is anticipated to be highly useful in the early diagnosis of pancreaticobiliary tumors [16]. We conducted this study to evaluate the efficacy of this device for the early diagnosis of pancreaticobiliary diseases, especially pancreatic malignancies.
In the present study, we recruited 148 patients scheduled for EGD screening (Table 1). We defined the minimum age as 50 years, because the prevalence of PC increases with age, especially in patients of ≥50 years of age [9]. As a result, a comparatively large number of findings are detected by procedures (Table 2). EGD screening revealed various findings, including reflux esophagitis, chronic gastritis, and gastrointestinal benign tumors, but not malignancies. The image quality of the CCD of the EG-580UR device is not equivalent to that of the latest endoscopes. In fact, to delineate the lesser curvature of the gastric angle when pulling back the scope was difficult in 56 patients (37.8%). This constructional disadvantage should be improved.
Various findings were detected by EUS screening. As shown in Table 2, pancreatic cysts, which were detected in 32 patients, were the most common finding.
Incidental pancreatic cysts are reported to be associated with increased mortality, and follow-up is recommended for patients in whom they are identified [20, 21]. IPMNs are pancreatic cysts that are associated a risk of malignancy; however, pancreatic cysts other than IPMNs may cause pancreatic ductal carcinoma [22]. Laffan et al. reported that the prevalence of unsuspected pancreatic cysts detected by MDCT in an outpatient population was 2.6%, which was correlated with increasing age and Asian race [23]. There are also some reports on the prevalence of pancreatic cysts on MRI imaging. De Jong reported that the prevalence was 2.4%, while Lee et al. and Zhang et al. reported that the prevalence was 13.5% and 19.6%, respectively [24-26].
EUS is undoubtedly a superior tool for the diagnosis of pancreatic diseases, including pancreatic cysts. Kamata et al. reported that the EUS was superior to other imaging modalities (e.g., CT or MRI) for the early detection of PC in patients with IPMN [27]. Pausawasdi et al. reported that EUS offered some benefits in the evaluation of pancreatic cyst [28]. They referred to the possibility of the molecular and biomarker analysis of cyst fluid obtained by EUS-FNA. Barresi et al. reported the efficacy of EUS-through-the-needle biopsy in pancreatic cystic lesions; however, this procedure is still in the investigational stage, because it is associated with a risk of needle tract seeding [29]. Additionally, contrast-enhanced EUS is reported to be an effective tool for the diagnosis of pancreatic cysts [30, 31]. We consider that EUS with high-resolution imaging can be a tool for identifying and qualitatively diagnosing pancreaticobiliary diseases.
Our result showed that the prevalence of pancreatic cysts was 21.6%, which was clearly higher in comparison to previous reports. This contradictory finding have been due to the fact that our cohort consisted of patients of ≥50 years of age. Actually, an autopsy study revealed that 24.3% of patients (most patients were ≥65 years of age) had pancreatic cysts [32]. Fortunately, there were no malignant findings, such as high-risk stigmata or IPMNs with worrisome features, and the patients with cysts of >5 mm in size were scheduled for follow-up MRI at six months. In our data, age and a history of diabetes mellitus were significantly associated with the prevalence of pancreatic cysts (Table 4).
Chronic pancreatitis is a risk factor for PC [33]. Recently, the early diagnosis of chronic pancreatitis with EUS has gained attention; however, the extent to which early chronic pancreatitis is associated with pancreatic carcinogenesis is still unclear [11, 34]. In our study, the prevalence of early chronic pancreatitis was 16.9%; this was related to a history of diabetes mellitus and smoking history (Tables 2 and 4). This result is in line with previous reports, and serves as a useful reference for identifying high-risk patients [24, 34, 35]. A family history of PC is a known risk factor for PC [37, 38]. There was no significant association between a family history of PC and the prevalence of pancreatic disease in this study. There may be some reasons for this controversial result. Canto et al. reported that individuals with three or more blood relatives with PC, including at least one first-degree relative, should be considered for screening [38]. In our study, there were 11 patients with only one affected first or second-degree blood relative. Additionally, the relatively small number of patients may have affected the result.
One patient had enlarged intra-abdominal lymph nodes, and was diagnosed with follicular lymphoma by EUS-FNA and 18-fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET). She was referred to a hematology specialist, and followed closely without chemotherapy.
The imaging capability of EUS was generally good (Table 3). However, these procedures were performed by experienced endosonographers. The technique of EUS imaging is sometimes difficult, and the diagnostic performance of EUS is operator-dependent. Increasing the number of endosonographers is also necessary to facilitate the early diagnosis of pancreaticobiliary diseases.
The screening method using the EG-580UR device is a little different from the traditional method using an ordinary EUS scope, especially with regard to duodenal manipulation, because this new scope has a slim distal end (11.4 mm) and a small bending radius. At first, this difference perplexed us; however, all operators soon got used to it. Actually, the imaging capability of EUS was generally good, and the procedure time was tolerable (Tables 3 and 4). Recently, curved linear array EUS scope is widely used. Radial scan EUS scope provides understandable organ image with 360°scanning range, however it cannot collect tissue samples. Kaneko et al reported that there was not a significant difference between the imaging capability of radial scan scope and curved linear array scope, however, both scope have pros and cons[39]. They reported radial scan scope was superior in the delineation of the major duodenal papilla and gallbladder. Front-viewing radial scan scope may be able to expand options for scope choice. Additionally, this scope and single-session EGD and EUS method may widen the training opportunities for novices. Increasing experts of EUS procedure using forward-viewing radial scan EUS scope may be conductive to improve pancreaticobiliary diseases.
The present study was associated with some limitations. The accuracy of the EUS findings was unclear because some participants did not undergo screening with other modalities (e.g., CT or MRI). Most patients were also scheduled for follow-up AUS, MRI or CT at six months; however, some patients who had no pancreaticobiliary findings did not wish to undergo the examination because of the high cost. Fortunately, there were no other pancreaticobiliary findings in 88 patients (59.5%) who—at the time of writing—have already undergone follow-up using AUS, CT or MRI. Additionally, the accuracy of EGD was still unclear. To date, 103 patients (69.6%) have already undergone follow-up EGD using a conventional EGD scope, and no other gastrointestinal findings were identified in follow-up EGD. It was unclear whether EUS was superior to other modalities; however, some patients were diagnosed with pancreatic diseases that could not be detected by post-AUS. This result proved the high sensitivity of EUS in the diagnosis of pancreatic lesions. These subjects should be evaluated in a future analysis with comparative design including large number of participants.
In this study, there was only one adverse event, which might have been caused by oversedation. We were concerned about the risk of increasing the dose of propofol; thus, we excluded patients with an ECOG performance status of 3 or 4. However, most procedures were completed within 30 minutes as a result. This might have been due to the normal EUS findings in most patients.