Endoscopic ablative therapy for biliary malignancy

Introduction
Cholangiocarcinoma, a malignancy of the epithelial cells in the intrahepatic or extrahepatic biliary tree, and gall-bladder cancer are often diagnosed at later stages. Median survival duration ranges from 3 to 9 months with a less than ten percent 5-year survival rate. Thus, often treatment strategies are aimed more towards palliation instead of cure ⁽¹⁾. Cholangiocarcinoma (CCA) has the highest incidence reported in Eastern and Southeastern Asia. The main risk factor of CCA in Asian countries is mostly linked to certain liver fluke infestation. Opisthorchis viverrini and Clonorchis sinensis have been associated with the development of CCA. CCA is a slow-growing neoplasm and during the early course of the disease, it runs a silent clinical course, therefore has notoriously been diagnosed late. Surgical resection offers the best curative treatment, but most of these patients are noted to be unresectable and are poor surgical candidates during the time of presentation. Thus, different endoscopic ablative modalities are currently on investigation to achieve this therapeutic goal.

Ablative modalities
With the majority of patients presenting with unresectable disease at the time of diagnosis, surgical intervention is not feasible, making less invasive endoscopic therapies more suitable. Initially, biliary stents were utilized for biliary decompression to mitigate cholestatic symptoms and prevent cholangitis; however, this strategy did not prove to provide significant survival benefit. Therefore, efforts to treat the tumor burden itself in addition to maintaining biliary patency became a focus of innovation and research in the endoscopic field. This has led to the advent of therapies such as photodynamic therapy, radiofrequency ablation, and intraluminal brachytherapy using Iridium-132 seeds. These options combined with biliary stenting have shown to not only offer the benefit of biliary decompression, but also to potentially improve stent patency and survival. Further, there is an anti-tumour effect of each of these modalities, portending an additional benefit in this subset of patients. The most exciting endoscopic ablative modality appears to be intraductal radiofrequency ablation using the Habib catheter and device inserted through the duodenoscope vis ERCP ⁽²⁾. Several case series have shown the effectiveness of this technique in ablating tumours. This technique is evolving and coupled with early diagnosis of CCA through cholangioscopy will allow for curative therapy.

Conclusions
Endoscopic ablative therapies for biliary malignancies are a promising tool. Despite numerous studies assessing these endoscopic ablative therapies, there is still a paucity of appropriately powered randomized controlled trials, and further research has yet to be done in the field.

References
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2. Roque J, Ho S-H, Reddy N, Goh K-L. Endoscopic ablation therapy for biliopancreatic malignancies. Clinical Endoscopy. 2015;48(1):15.