Clinical outcomes and dosimetric characteristics of salvage transvaginal HDR-ISBT for centrally recurrent pelvic gynecologic malignancies after prior radiotherapy: a single-center retrospective study

This study aimed to evaluate the efficacy and safety of transvaginal high-dose-rate interstitial brachytherapy (HDR-ISBT) in patients with centrally recurrent pelvic gynecologic malignancies after prior radiotherapy, and to explore the dosimetric and clinical outcomes between 3D-printed template (3D-PT)-assisted and freehand implantation. A total of 27 patients with centrally recurrent pelvic gynecologic malignancies treated with transvaginal HDR-ISBT between January 2018 and December 2023 were retrospectively analyzed, including 16 cases treated with 3D-PT-assisted implantation and 11 with freehand implantation. Dosimetric parameters, objective response rate (ORR), local progression-free survival (LPFS), overall survival (OS), and treatment-related toxicities were assessed. The ORR was 85.2%, with a complete response (CR) rate of 48.1%. In the entire cohort, the 1-, 3-, and 5-year LPFS rates were 46.7%, 35.0%, and 26.3%, respectively, with corresponding OS rates of 96.0%, 72.5%, and 72.5%. HR-CTV D90 (EQD2) < 51 Gy was associated with poorer LPFS. Compared with the freehand group, the 3D-PT group achieved higher HR-CTV D90 and V100. The deviation between delivered and prescribed HR-CTV D90 (EQD2) was more tightly distributed in the 3D-PT group. No significant differences were observed between the 3D-PT and freehand groups in ORR, LPFS, or OS. No grade ≥3 acute toxicities were observed, while grade ≥3 late toxicities occurred in 18.8% of the 3D-PT group and 36.4% of the freehand group. Transvaginal HDR-ISBT appears to be a feasible salvage treatment option for centrally recurrent pelvic gynecologic malignancies after prior radiotherapy. 3D-PT-assisted implantation was associated with improved dosimetric parameters. Given the limitations in confounder adjustment and the small sample size, these findings should be interpreted as hypothesis-generating.