Background: Self-expanding metal and plastic esophageal stents (SEMS and SEPS, respectively)
are used in conjunction with chemoradiation for palliation of malignant dysphagia.
To date, the dosimetric effects of stents undergoing proton radiotherapy are not known.
Study aim: To investigate the proton radiotherapy dose perturbations caused by esophageal stents
of varying designs and materials undergoing external beam treatment for esophageal
cancer.
Patients and methods: Simulated clinical protocol. Solid acrylic phantom was used to mimic the esophageal
tissue environment. Stents made of nitinol, stainless steel and polyester were tested.
Proton beam dose of 2 Gy-E was delivered to each stent in a single anterior to posterior
field. Film and image based evidence of dose perturbation were main outcomes measured.
Results: Only the stainless steel and plastic stents demonstrated slight overall dose attenuations
(– 0.5 % and – 0.4 %, respectively). All the nitinol-based stents demonstrated minimal
overall dose perturbations ranging from 0.0 % to 1.2 %. Negligible dose perturbations
were observed on each of the stent surfaces proximal to the radiation source, ranging
from – 0.8 % (stainless steel stent) to 1.0 % (nitinol stent). Negligible dose effects
were also observed on the distal surfaces of each stent ranging from – 0.5 % (plastic
and stainless steel stents) to 1.0 % (nitinol stent).
Conclusion: Proton radiotherapy dose perturbations caused by stents of varying designs and material
composition are negligible. Negligible dose perturbation is in keeping with the inherent
advantage of proton therapy over traditional radiotherapy composed of photons – given
its relative large mass, protons have little side scatter.
