Our study is the first to describe and compare the long-term clinical efficacy of FC-SEMS vs. plastic stent placements in a clinical setting for treatment of persistent MPD strictures in CP patients. Although FC-SEMS showed typical delayed complications such as de novo stricture and spontaneous migration, its clinical efficacy showed higher MPD stricture resolution rate and considerable sustained pain relief during follow-up.
FC-SEMS not only has a larger diameter and longer patency than a plastic stent, but it is technically easier to release than even a single plastic stent due to its superior “pushability,” with higher flexibility and a lower external diameter of the pushing catheter (7Fr vs. 10Fr)7,8. Technically, all FC-SEMSs were successful in insertion and removal, including three stent fracture cases and two proximal migration cases. Furthermore, the larger diameter of FC-SEMS can help improve MPD stricture. According to previous studies, stricture resolution was achieved in 83-100% of patients treated with FC-SEMS 8-11,13 and in 9-50% of patients with single plastic stenting5,14-17. Similarly, we observed more MPD stricture resolution in the FC-SEMS group (87.0% vs. 42.0%, p < 0.001), although stent placement duration was significantly shorter in the FC-SEMS group than in the plastic stent group (4.9 vs. 7.3 months, p = 0.022).
Temporary placement of FC-SEMS, together with surgery and multiple side-by-side plastic stent placement, is currently considered a treatment option for refractory MPD strictures3. Clinical results of FC-SEMS obtained from several prospective studies were described in Supplement Table 2. When comparing clinical data of FC-SEMS placement for symptomatic MPD strictures in CP patients, several complicated and discordant issues remain. First of all, clinical indication for FC-SEMS placement is variable. Some early studies enrolled all symptomatic MPD stricture patients, independent of plastic stent placement before FC-SEMS insertion8,13. By contrast, other studies, including our study, have included only persistent or refractory stricture patients with inclusion criteria of a 39,11 or 12 month10 duration of previous plastic stent placement. When the FC-SEMS group was divided into before and after plastic stent indwelling period of 6 months for subgroup analysis in our results, the FC-SEMS group under 6 months of plastic stent indwelling (n=13, 50.0%) showed comparable clinical efficacy of MPD stricture resolution, recurrence rates and pain relief during follow-up (91.7% vs. 81.8%, p=0.484; 80.0% vs. 66.7%, p=0.484; 84.6% vs. 69.2%, p=0.352, respectively) compared with the remainder subgroup (n=13, 50.0%). Because the evidence for FC-SEMS is currently lacking, further clinical trials is needed on the indications and timing of FC-SEMS placement in CP patients.
Notably, spontaneous migration developed in one-fourth (26.9%) of FC-SEMS group patients, and other delayed complications such as stent fracture (7.7%) and de novo stricture (23.1%) were also prevalent (p = 0.002, 0.039, and <0.001, respectively). However, all of the stent fractures were partially broken and could be endoscopically removed at once. De novo strictures were also clinically manageable by additional plastic stenting in our experience. Reported frequencies of stent migration and de novo strictures for FC-SEMS are 15%–46% and 16%–27%, respectively9,11,13,18 (Supplement Table 2). Tringali et al. reported that the short length of 3 cm-long FC-SEMS may be associated with frequent stent migration11, and Oh et al. suggested that additional anchoring inner plastic stents help to prevent stent migration10. Anti-migration systems have been recently developed and applied to FC-SEMS18,19, but some concerns exist due to its flared end, which may cause stent-induced de novo stricture9,11,13,18.
Our study has several limitations. First, this was a non-randomized retrospective study. Although statistically not significant, patients with active drinking and other CP complications such as PD stones and pseudocysts may suffer more frequently, and relatively long follow-up duration in plastic stent group (36.2 vs 24.9 months, p = 0.237) was likely to be associated with frequent pain aggravation during follow-up. Changes in endocrine and exocrine functions were also not comparable for both groups during the stent placement period. In addition, the stent features of FC-SEMS and plastic stents were not unified, and there was no consistent strategy for choosing FC-SEMS or plastic stents. In the plastic stent group, 19 patients (35.2%) were unable to upsize the diameter of plastic stent, and about three-quarters (74.1%) of patients contained the single plastic stent with a diameter of lesser than 8.5Fr until the last follow-up (Table 1). Larger diameter (10Fr vs. ≤8.5Fr) and multiple plastic stent placements have been considered more effective endotherapies than smaller single plastic stents20-22. Some patients treated with plastic stents sub-optimally can affect less effective clinical outcomes in the plastic stent group. Last, we analyzed cost-effectiveness simply due to our relatively small study population, excluding length of hospitalization and complication rates.
In conclusion, FC-SEMS placement for persistent MPD stricture in CP patients had favorable long-term clinical efficacy with higher MPD stricture resolution rate and sustained pain relief during follow-up than plastic stenting. As typical complications of FC-SEMS such as de novo stricture and spontaneous migration remain major issues, further investigation is needed to resolve these problems.