Ultrasound screening for cholangiocarcinoma could detect premalignant lesions and early-stage diseases with survival benefits: a population-based prospective study of 4,225 subjects in an endemic area

Cholangiocarcinoma is a tumor of the biliary tract, presumably of cholangiocytic origin, with a rising global incidence [1‐6]. Several known risk factors exist, linking chronic biliary inflammation to the pathogenesis of cholangiocarcinoma [7, 8]. Late presentation to hospital, with a median survival of months, is noted in most patients in developing countries whereby cholangiocarcinoma is most prevalent. Moreover, the pathological or cytological diagnosis of cholangiocarcinoma is not always accessible despite indications from imaging studies and clinical condition [7‐10]. Surgical resection is the current therapy of choice for every type of cholangiocarcinoma [8, 11, 12]. Resection offers the best opportunity for long-term survival. Nevertheless, in the minority of patients and in those with large node-positive or multifocal intrahepatic cholangiocarcinoma, resection seems to provide little benefit [10, 12]. Overall, the 5-year survival in cholangiocarcinoma cases is poor, with 60 % to >90 % recurrence rates [7, 9, 13].

Cholangiocarcinoma is relatively rare in most western countries, but high incidence rates have been reported in Eastern Asia, especially in Thailand [5, 14‐16]. The etiology of this cancer appears to be mostly due to specific infectious agents [17, 18]. In 2009, infections with liver flukes, Clonorchis sinensis or Opisthorchis viverrini, were both classified as carcinogenic to humans by the International Agency for Research on Cancer for cholangiocarcinoma [14, 18]. With the current systematic tumor registration in Thailand, new high-incidence areas have been identified in North and Northeastern Thailand [10, 17, 19]. Ban Luang is a district in the western part of Nan Province in Northern Thailand and is divided into 4 sub-districts. Based on a previous study, the incidence of liver cancer in Ban Luang was 138.8 per 100,000 persons, which is higher than that of other regions of the world or even in Khon Kaen Province, which is previously reported as an endemic area for cholangiocarcinoma [17, 20, 21].

The present study aimed to ascertain the prevalence and incidence of cholangiocarcinoma, to identify predisposing factors, and to explore whether screening could lead to early treatment and reduction of morbidity and mortality rates of cholangiocarcinoma patients.

Cholangiocarcinoma is a silent malignancy with a significantly high morbidity and mortality. Patients usually present at a late stage, rendering curative measures impossible to be performed to prolong lives [9, 13]. Although the annual incidence rate of cholangiocarcinoma in the western countries is low at 1–2 cases per 100,000, many studies have documented a steady increase in the incidence of intrahepatic cholangiocarcinoma over the past few decades; increases have been seen in North America, Europe, Asia, and Australia [2, 4, 6]. Our study confirmed a high prevalence and high incidence rate of cholangiocarcinoma in Thailand, particularly in the northern region of the country with a prevalence rate of 165.7 per 100,000 and 1- and 2-year incidence rates of 236.7/100,000 and 520.7/100,000, respectively [10, 17].

As a screening program for cholangiocarcinoma is currently not established worldwide, this study was intended to explore if abdominal ultrasonography or tumor markers could be of benefit to detect early-stage cases for curative intent in an endemic area. By performing successive ultrasonography every 6 months, we managed to identify 32 cholangiocarcinoma cases from 1 to 6 sessions over a 3-year period and 65 % of our patients were diagnosed with early-stage and operable tumors which was markedly different from all the hospital-based data previously reported in Thailand whereby most cholangiocarcinoma cases presented at a late stage. A recent study from the National Cancer Institute of Thailand showed that there were 2.17, 12.69, 24.77, and 57.89 %, respectively, of stage I, II, III, and IV of newly diagnosed cholangiocarcinoma cases diagnosed at their institute in 2013 [23]. Nevertheless, the most common tumor location in this study was intrahepatic which was similar to other published hospital-based studies [7, 12, 24].

Over a follow-up period of 3 years, 1- and 2-year survival rates of the affected cases were high (>60 %), particularly in resectable cases (100 and 78 %, respectively) as expected, and were much better than those reported from previous studies in Thailand and Malaysia with advanced and inoperable cases [10, 11, 25]. Outcome data from a study in Khon Kaen of 411 intrahepatic cholangiocarcinoma patients revealed that only 138 cases were resectable and the mean survival time was 1,039 days in tumor stage III, 773 days in stage IVa, and 382 days in stage IVb [10]. Rare long-term survival with a one-year survival of just 15 % was reported in perihilar cholangiocarcinoma cases [11]. Another long term follow-up data from Malaysia in 69 cholangiocarcinoma patients showed that the overall median survival was 4 months with the median survival of 16 months in R0 resected patients [25]. Overall 1-, 2- and 3-year survival rates were 67, 17 and 17 %, respectively. In one study from the US, 53.8 % of newly diagnosed intrahepatic cholangiocarcinoma patients were not candidates for resection [12]. In resectable groups, the median disease-specific survival was 36 months and recurrence was observed in most of the patients (62.2 %). In unresectable groups, the median survival varied depending on modalities of treatments, i.e., 22 months and 9 months in patients receiving regional chemotherapy as part of treatment and systemic chemotherapy alone, respectively. Although our outcomes could not be directly compared because other reports were from hospital-based studies, it is evident that screening ultrasonography could identify patients at an early and asymptomatic stage leading to better treatment outcomes.

Interestingly, our study identified 11 patients with premalignant lesions (stage 0) such as biliary intraepithelial neoplasia, intraductal papillary biliary neoplasm or dysplastic epithelium [26]. Our pathological results were achievable because we detected patients at the earliest stage whereas most studies of cholangiocarcinoma did not have pathological tissue due to the inoperative nature of the late-stage cases. These premalignant lesions represent cases whereby abnormal cells were found in the innermost layer of the tissue lining of the extrahepatic bile duct. All of them did better than the early-stage cholangiocarcinoma cases with 100 % DFS and are still alive at 3-year follow-ups. Therefore, patients detected at a premalignant stage appeared to benefit the most from screening ultrasonography and potentially are cured.

With regards to demographic data, the population in Ban Luang is socioeconomically comparable to rural northern and northeastern population of Thailand with similar ethnic backgrounds [27]. The villagers’ major occupation was farming with an average income per month of 1,000–4,999 THB (about 30–145 USD). The mean age of cholangiocarcinoma cases of 51.9 years old in this study was consistent with the average age of cholangiocarcinoma cases reported from the National Cancer Registry or hospital-based studies [28] but was much lower than most western data whereby most patients are in their 60s or 70s [2, 4, 13]. During our 3-year study period, no cancer patients under the age of 40 years old were identified. Hence, age could be another factor in disease development and cholangiocarcinoma screening in individuals younger than 40 years old may not be of value or necessary in an endemic area. Similar to some previous data, the prevalence of cholangiocarcinoma was slightly higher in males as compared to females [29, 30]. Other significant demographic data was a history of alcohol drinking and a family history of liver cancer in the cholangiocarcinoma cases as compared to non-cancer cohort, which could be important for the development of cholangiocarcinoma. In addition, we found a strong family history of cholangiocarcinoma in some patients. Cholangiocarcinoma patients had many first-degree relatives with liver cancer although most of them were diagnosed only by clinical suspicion, for example, obstructive jaundice with abdominal mass, mostly without histological confirmation.

Although risk factors for the development of cholangiocarcinoma in the western countries are primary sclerosing cholangitis, an inflammatory disease of the biliary tract, and ulcerative colitis, certain parasitic liver diseases are notable risk factors in Asia. Colonization with the liver flukes O. viverrini (in Thailand, Laos and Vietnam) [31‐33] or Clonorchis sinensis (in China, Taiwan, Eastern Russia, Korea, and Vietnam) is associated with the development of cholangiocarcinoma [34]. In this study, we found that about 18–25 % of our villagers had a history of liver flukes and 25–35 % of them had been treated with drugs to eradicate the parasites but no significant difference was observed between the cancer cases and the non-cancer cases. There are many potential problems with detecting O. viverrini eggs by microscopic examination. For example, the egg features are similar to those of lecithodendrid and heterophyid parasites, therefore, the examination requires a high level of skill, and the methods are time consuming. To overcome these constraints, with the cooperation of the Department of Helminthology, Faculty of Tropical Medicine, Mahidol University, stool internal transcribed spacer (ITS)-PCR, which is a more sensitive and specific method, was performed in 22 cholangiocarcinoma patients during the first 2 years of the study [35]. All patients had positive results from stool PCR for O. viverrini, suggesting that O. viverrini continues to be an important contribution factor to the development of cholangiocarcinoma in Thailand.

Although we could detect early-stage disease and the majority of patients were able to receive curative surgery, the recurrence rate was still not as low as expected, necessitating our attempts to identify if tumor markers could be of better benefit than ultrasonography for early screening. Our study confirmed that currently available tumor markers have inadequate sensitivity and specificity for cholangiocarcinoma screening [36, 37]. These markers, such as CEA, CA 19–9, ALP, were not sensitive enough to detect early cholangiocarcinoma cases in our study cohort. Other new biological markers may be needed to identify patients at the earliest stage that will potentially lead to curative success [35, 38, 39]. Nevertheless, with the excellent outcome of our patients with premalignant lesions, we suggest that ultrasonography should be a first screening tool for cholangiocarcinomain an endemic area until other useful biological markers are discovered or become available. Studies are ongoing to identify new genomic and proteomic markers for cholangiocarcinoma cases in Thailand [40]. New therapeutic advances are also needed to improve the disease-free survival of patients undergoing surgical resection [41, 42].

This study represents the first large population-based screening program ever performed in an endemic area of cholangiocarcinoma by serial ultrasonography coupled with laboratory tests. The high prevalence and incidence rates of cholangiocarcinoma in Northern Thailand were evident. Current tumor markers and stool examination for parasites are not of benefit for cholangiocarcinoma screening in an endemic area. Ultrasonography should be offered as a first screening tool for cholangiocarcinoma in individuals aged ≥40 in an endemic area. Patients with premalignant lesions achieved the most benefit from screening ultrasonography and are potentially cured. Future studies are needed to identify new biological markers that will capture cancer cells at the earliest stage of development.

AFP, α-fetoprotein; ALP, alkaline phosphatase; CA 19–9, carbohydrate antigen 19–9; CBC, complete blood count; CCA, cholangiocarcinoma; CEA, carcinoembryonic antigen; CT, computed tomography; DFS, disease-free survival; H&E, hematoxylin and eosin; ITS, internal transcribed spacer; IU, international unit; LFT, liver function tests; mL, millilitre; mm, millimeter; MRCP, magnetic resonance cholangiopancreatography; MRI, magnetic resonance imaging; ng, nanogram; NPV, negative predictive value; O. viverrini, Opisthorchis viverrini; OS, overall survival; PCR, polymerase chain reaction; PFS, progression-free survival; PPV, positive predictive value; U, unit.