The Fabrication of an Acrylic Repositioning Stent for Use During Intensity Modulated Radiation Therapy: A Feasibility Study.

Abstract

Radiotherapy is one of the main treatment modalities for head and neck cancers. To minimize damage to normal tissues during radiotherapy, various methods of stabilization have been used, including thermoplastic facemasks and repositioning stents. The goal is to assess the effect of using a customized oral repositioning stent on patient positioning during the course of radiotherapy. Ten consecutive patients scheduled to undergo intensity modulated radiation therapy (IMRT) for cancers of the maxillary sinus, nasal cavity, or oral cavity were recruited to participate in the study (ST group). These patients were matched to 2 retrospective cohorts, one using the original repositioning stent design (OB group), and the other with no stabilization stent (NB group). Hard baseplate wax was used to create a customized wax pattern of the proposed acrylic stent chairside, and processed in heat-cured clear hard acrylic. Relative stability of the daily patient setup was assessed by comparing measurements from surrogate bony landmarks to radiation isocentres obtained from the initial reconstructed planning computed tomograph (CT) to each daily KeV image. There was no stent fracture or distortion throughout treatments, and no patients' treatments were required to be aborted, delayed, or replanned. Mean 3D deviations for the ST, OB, and NB groups were 0.29 ± 0.10 cm, 0.32 ± 0.14 cm, and 0.31 ± 0.13 cm, respectively. The ANOVA test revealed no significant difference in triangulated variations between the treatment groups (F = 0.18, p = 0.84). Patient stability data demonstrated mean vertical, longitudinal, and lateral variations that did not appear different when compared to 2 retrospective cohorts. Although the deviations were not statistically significant between matched cohorts, the added durability of the stent and comfort for patients, without affecting IMRT timeline, are considered clinically significant. By using a customized repositioning stent, it is possible to maintain patient stability comparable to prior protocols and within the range of clinical guidelines, while providing superior comfort and ease of insertion to the patients.