Response

On behalf of our co-authors, we would like to express our appreciation for the comments made by Li and Liu about our study. Those authors point out that the longer length of the malignant stricture in partial covered double bare metal stent (PCDBS) could lead to a significant difference in the higher incidence of tumor overgrowth in the PCDBS group. As they pointed out, the length of stricture in the PCDBS group was longer than that in the uncovered double bare metal stent (UCDBS) group (2.8 ± 1.3 vs 2.4 ± 1.2; p = .010). However, the stent lengths for both groups were not meaningfully different (7.0 [6.0-8.0] vs 6.0 [6.0-7.0]; p = .430). Therefore, the differences in stricture length in both groups could not affect the duration of stent patency. Furthermore, the results of our study are completely in accord with those of previous comparative studies^{,  ,}  between single-layer covered stents and uncovered stents. In general, the rate of ingrowth is less in covered stents because of the membrane-covered mesh of the stent, whereas this benefit may be offset by the increased rate of overgrowth at the edges of the covered stent. Consequently, the difference in stent overgrowth between PCDBS and UCDBS can be attributed to the characteristics of membrane. In addition, selection bias is generally defined as the bias introduced by the selection of individuals, groups, or data for analysis in such a way that proper randomization is not achieved, thereby failing to ensure that the sample obtained is representative of the population intended to be analyzed. Our study is the largest randomized trial to compare covered stents with uncovered stents, and consecutive patients were included by strict criteria. Therefore, there is only a slim chance that selection bias affected of our study. In terms of the total incidence of a single adverse event (AE), which was not addressed in our study, we have data, summarized as Table 1. Total AEs after ERCP were noted in 58 patients (45.3%) in the PCDBS group and 63 patients (49.6%) in the UCDBS group, without significant differences (p = .575), and the AEs were minute in clinical situations.

We also agree with the opinion of Li and Liu that an adjunctive procedure such as radiofrequency ablation, photodynamic therapy, or another local ntitumor therapy can have some influence on stent patency and overall survival. However, to maintain the consistency of the study, we did not perform additional interventions to prolong stent patency. In detail, our strategy of revision for stent dysfunction included only stent exchange with or without removal of a previously inserted stent by endoscopic or percutaneous approaches, permanent percutaneous catheter placement, or palliative surgical revision. In addition, stent patency in our study was defined as the interval between the time of stent placement and the time of first reintervention caused by to stent dysfunction. Thus, adjunctive local antitumor therapy during a first revisional procedure could not have affected the stent