MSOR12 Presentation Time: 5:55 PM

Abstract

Purpose

This single-institution proof of concept and early experience on an innovative workflow for the creation of custom applicators for high dose rate (HDR) skin brachytherapy and skin bolus in low to middle-income countries, where access to CT simulation or dedicated surface scanners is sparse, we utilized geometry mapping technology found in many readily available smartphones as an alternative to other design methods, reducing the number of CT-simulations needed from two to one, improving access to custom applicators for more patients. We now report our skin brachytherapy early experience.

Materials and Methods

In selected consenting patients with indication for skin brachytherapy or EBRT, a smartphone front camera system (e.g. Apple iPhone X or newer with TrueDepth camera) was used to capture the skin surface with capturing software (Apple iOS - Heges 3D Scanner by Marek Simonik), then exported to a computer-aided design software to blueprint the applicator (Meshmixer and Fusion 360 Autodesk on Apple MacOS or Microsoft Windows). The applicator was then 3D printed in-house using a fused deposition modeling printer (Flashforge Adventure 3) with polylactic Acid (PLA) material. The applicator completed a quality assurance examination and then fitted to the patient for a single CT simulation for planning (SagiPlan®), quality assurance and treatment delivery with a Cobalt - 60 after loader (SagiNova®). Follow-up was conducted per standard institutional protocol, and Common Terminology Criteria for Adverse Events Version 5.0 (CTCAE) was used to report toxicities.

Results

From July 2023 to January 2024, 05 patients were scanned, 4 patients received a 3D printed custom bolus for EBRT, and 1 patient received a custom HDR skin brachytherapy custom applicator, the one patient treated with HDR brachytherapy is reported, had basal cell carcinoma of the nose, the prescription dose was 40Gy in 10 fractions delivered daily, 100% isodose line encapsulated the PTV, limiting surface dose <150%. Acute grade 1 skin toxicity was observed at the end of treatment, it completely resolved at 3 months. No late toxicity or recurrence was observed at 6 months.

Conclusions

This small, early-reported experience with a novel workflow seems faceable and safe, potentially allowing less congestion at the CT Sim, improving access for more patients in low to middle-income countries to custom 3D printed accessories. A larger number of patients and longer follow-ups are needed, report on 3D EBRT bolus results to follow.