What exactly shortens stent patency in hilar block from gallbladder carcinoma?

Our group has read with interest the recent paper by Miura et al. entitled “Risk factors for recurrent biliary obstruction following placement of self-expandable metallic stents in patients with malignant perihilar biliary stricture” [1]. We appreciate this work and publication very much, and would like to make some comments regarding the paper.

The authors reported that gallbladder cancer was significantly associated with shorter stent patency. Gallbladder cancer was defined as “a primary lesion in the gallbladder that invaded to the perihilar portion.” Thus, the patients with gallbladder cancer in this study must have been at a very advanced stage, which is usually the case in daily practice [2] [3]. The poor prognosis of gallbladder cancer was confirmed recently in a large epidemiologic study, which showed that the median survival times for extrahepatic cholangiocarcinoma and gallbladder cancer were 11.3 and 6.4 months, respectively [4]. Miura et al. used recurrent biliary obstruction (RBO), or patient death for those with no RBO, to determine stent patency, as shown in Fig. 4 of the paper (only 12 patients with gallbladder cancer were shown in the analysis).

We wonder how many patients with gallbladder cancer actually developed RBO. It appears that the patients with gallbladder cancer had a very poor prognosis and that the majority of them died before stent occlusion. Therefore, by the original definition of stent patency, which censored at the date of death as one of the criteria, there might be a certain number of patients with gallbladder cancer who had short survival but were included and analyzed with RBO. The authors helpfully performed an additional analysis, which combined both RBO and patient death as the end point; however, this could not explain the situation. To clarify this point, we would like the authors to detail how many patients with gallbladder cancer developed RBO. This would also help to emphasize the importance of their discussion point in which they recommend avoiding insertion of metallic stents in patients with gallbladder cancer because of the risk of tumor ingrowth and the difficulty in preventing such ingrowth.

• References

• 1 Miura S, Kanno A, Masamune A et al. Risk factors for recurrent biliary obstruction following placement of self-expandable metallic stents in patients with malignant perihilar biliary stricture. Endoscopy 2016; 48: 536-545
• 2 Hundal R, Shaffer EA. Gallbladder cancer: epidemiology and outcome. Clin Epidemiol 2014; 6: 99-109
• 3 Boutros C, Gary M, Baldwin K et al. Gallbladder cancer: past, present and an uncertain future. Surg Oncol 2012; 21: e183-191
• 4 Flemming JA, Zhang-Salomons J, Nanji S et al. Increased incidence but improved median overall survival for biliary tract cancers diagnosed in Ontario from 1994 through 2012: a population-based study. Cancer 2016 in press DOI: 10.1002/cncr.30074