A novel free-assembled template for interstitial brachytherapy of locally advanced cervical cancer: a dosimetric study

Background The application of guidance template in interstitial brachytherapy (ISBT) was expected to improve target coverage and sparing organs at risk for locally advanced cervical cancer (LACC). The purpose of this study was to compare dosimetric and procedural outcomes of template-guided ISBT against free-handed ISBT. Methods Consecutive patients with LACC were prospectively enrolled at Sichuan Cancer Hospital from February to September 2025. A novel 3D-printed free-assembled interstitial template (FAIT), featuring a tandem with optimized non-coplanar needle channels, was invented and utilized for ISBT. Each patient underwent both FAIT-guided and free-handed high-dose-rate ISBT within 3 days with a random sequence. Treatment plans were generated in the Oncentra planning system with a 600 cGy prescription, and dosimetric parameters including high-risk clinical target volume (HRCTV) D ₉₀ , dose of organs at risk (OARs) (D _1cc and D _2cc for bladder, rectum, sigmoid and bowel) were extracted. The number of interstitial needles and implantation time were also recorded. Data were presented as mean ± standard deviation and compared using paired Student’s t -tests. Statistical significance was defined as P  < 0.05. Results 55 patients received both FAIT-guided and free-handed ISBT procedures after pelvic external beam radiotherapy (EBRT) of 45-50.4 Gy with 25–28 fractions. Most patients were stage ⅡB (n = 34, 61.8%) and squamous cell carcinoma (n = 49, 89.1%), and mean post-EBRT HRCTV volume was 61.8 ± 21.3 cm ³ . There was no significant difference on the number of needles used in FAIT-guided and free-handed ISBTs (4.88 ± 0.90 vs. 4.76 ± 1.24, P  = 0.30). FAIT guidance shortened implantation time (5.83 ± 1.93 vs 8.03 ± 2.71 min, P < 0.0001) and achieved higher HRCTV D90 (611.38 ± 35.12 vs 580.86 ± 64.65 cGy, P < 0.01), with similar OAR doses (P > 0.05). Conclusions Improved target volume dose coverage and shortened needle implantation time were achieved with the application of the novel 3D-printed FAIT in ISBT. This novel template had high clinical utility and was worthy of further promotion and application.