Background: A surprisingly low number (< 20%) of relevant (> 75%) restenoses occur in exophytic lesions after treatment with uncovered metal stents. The goal of this study was to investigate whether radial stent forces can exert localized influence on tumor growth.
Patients and methods: In 17 patients, intraluminal tumor tissue was histologically investigated before and 1 week after stent implantation. The amount of intact tumor cells (ITCs) was compared to necrotic and nontumor cells. The result in patency was proved by fiberoptic bronchoscopy.
Results: Initially, stenoses in all patients were > 75%. Before stent implantation, biopsy samples in seven patients showed > 67% ITCs, and five patients had 34 to 67% ITCs. Five patients had 1 to 33% ITCs, and no patients had 0% ITCs. One week after stent implantation, the cellular aspect of the biopsy samples had changed significantly (p < 0.03): two patients had > 67% ITCs, one patient had 34 to 67% ITCs, and seven patients had 1 to 33% ITCs. Seven patients had no ITCs at all. Endoscopically, patency increased significantly (prestent, 10 ± 14.1%; poststent, 90.6 ± 14.3% [mean ± SD]; p < 0.0001).
Conclusion: Pressure exerted by the stent on adjacent tumor tissue may cause a profound reduction in the amount of ITCs, most probably caused by radial and shear stress forces that compromise blood supply and nutrients of the tumor stroma.