Collaborative design and additive manufacturing of a patient-specific high-dose-rate surface mold applicator for upper lip plesiotherapy.

PURPOSE: To demonstrate the use of additive manufacturing in the design and fabrication of a high-dose-rate (HDR) plesiotherapy applicator for upper lip squamous cell carcinoma, with emphasis on design parameters, adequate dose coverage, and practical considerations for applicator customization.

MATERIAL AND

METHODS

A 52-year-old male with persistent superficial upper lip squamous cell carcinoma, who previously underwent definitive chemoradiotherapy, was selected for HDR plesiotherapy boost to residual disease in an under-dosed region. Clinical measurements were performed by computer-aided design (CAD) for patient-specific surface mold incorporating pre-defined catheter geometry and mechanical features, to ensure applicator stability despite severe trismus. The applicator was fabricated using fused deposition modeling in flexible thermoplastic polyurethane (TPU). Dimensional verification, catheter patency testing, and clinical fitting were followed by conventional CT-based treatment planning.

RESULTS

The applicator was designed and fabricated within 72 hours, and radiotherapy planning followed GEC-ESTRO recommendations. Treatment planning achieved adequate target coverage, with high-risk clinical target volume (HR-CTV) D90 > 100% of prescription and V100 > 90% while maintaining acceptable dose homogeneity (DNR: < 0.36, DHI: > 0.70). Applicator positioning was reproducible across fractions, and verified by daily clinical examination and image verification. Treatment delivery was completed without device-related complications.

CONCLUSIONS

This report demonstrates the integration of additive manufacturing into a clinical brachytherapy workflow for a patient with upper lip squamous cell carcinoma, allowing fabrication of a patient-specific surface mold applicator with technical advantages in geometric accuracy and conformity to site-specific anatomic and functional constraints. Broader clinical implementation will require structured workflow integration, institutional planning of additive manufacturing logistics with in-house versus external production, standardization of quality assurance processes, and validation in larger clinical cohort studies.