3D-printed oral stents improve setup stability, geometric morphology, and dosimetric outcomes while reducing functional impairment in radiotherapy for nasopharyngeal carcinoma.

OBJECTIVE

To evaluate whether personalized three-dimensional (3D)-printed intraoral stents improve functional outcomes and setup reproducibility in nasopharyngeal carcinoma (NPC) radiotherapy without compromising dosimetric fidelity.

METHODS

This retrospective study included 99 NPC patients treated with definitive VMAT between January 2023 and December 2024. Patients were divided into stent group (n = 48) who wore 3D-printed intraoral stents during radiotherapy, and control group (n = 51) who received no intraoral device. Radiation-induced toxicities (xerostomia, dysgeusia, dysphagia, hearing loss) were assessed via telephone questionnaire. Interfractional setup reproducibility of organs at risk (OARs) was evaluated using daily cone-beam CT, and dosimetric parameters (D2, D98, Dmean) were compared between groups.

RESULTS

Stent use was significantly associated with reduced incidence and severity of hearing loss, dysgeusia, xerostomia, and dysphagia (all P < 0.05). Interfractional geometric variability of parotids and tongue was significantly reduced in the stent group (P < 0.05), indicating improved geometric stability. Post-hoc dosimetric analysis revealed significantly lower inner ear doses (Dmean/Dmax) in the stent group (P < 0.05), providing a dosimetric basis for hearing preservation.

CONCLUSION

Patient-specific 3D-printed intraoral stents confer clinically meaningful benefits in NPC radiotherapy by improving functional preservation and interfractional setup reproducibility. These benefits appear driven by two complementary mechanisms: direct dose sparing of fixed OARs (inner ear) and enhanced geometric stabilization of mobile OARs (tongue, parotids). These findings support integrating such stents into routine practice to reduce toxicity without compromising planned dose delivery.