Silicone tube stents have been believed to migrate more often, but this has been based on anecdotal evidence, and no prior studies have identified or quantified the risk using incidence rates. Because silicone stents are easier to remove than expandable metal stents, quantifying the magnitude of the risks and benefits allows physicians to take these factors into consideration when choosing a stent. The advantages of easier removability are important when considering benign disease, but for patients with advanced cancer the benefits of lower migration rates may outweigh concerns regarding removal.

Table 1—Multivariate Extended Cox Model of Time to Granulation Tissue Formation

Characteristic Hazard Ratio 95% CI P Value
Dumon silicone vs Ultraflex 3.32 1.59-6.93 .001
Aero vs Ultraflex 1.60 0.61-4.21 .34
Infection: yes vs no (time 5.69 2.6-12.42 < .001

We also found higher incidence rates of granulation tissue with silicone and Aero stents than with Ultraflex stents. Self-expanding metal stents have been believed to lead to more granulation tissue than silicone stents, but again this has been based on anecdotal evidence only.

We believe the observed differences in granulation tissue may be related to repetitive motion trauma and infection. Repetitive stent motion may cause trauma, with mucosal inflammation and granulation tissue formation. Histologic studies of stents have shown a nonspecific inflammatory response without foreign-body giant cells. Presumably, stents with higher migration rates also have a higher degree of motion, putting them at increased risk for developing granulation tissue. This is consistent with our observation that silicone stents have a higher incidence of both migration and granulation.

Bacterial infection may also play a role in granulation tissue formation. The available evidence supporting this is limited, with most of the data coming from studies of laryngotracheal reconstruction, tracheal stenosis, and subglottic stenosis.