Development and Assessment of Interstitial Brachytherapy Using Individual Curved-Needle in Treatment of Recurrent Gynecological Tumors After External Beam Radiotherapy.

IntroductionTo evaluate the efficacy and safety of individualized curved-needle interstitial brachytherapy (ISBT) using 3D printing for recurrent gynecologic tumors.MethodThis retrospective observational study enrolled patients with pelvic recurrent gynecologic tumors from March 2022 to April 2024. All patients received external beam radiotherapy (EBRT) (40-60 Gy, 20-30 fractions), followed by individualized curved-needle ISBT using a 3D-printed applicator (12-30 Gy, 2-5 fractions). Concurrent systemic therapy was administered when necessary. Dosimetric parameters (V100%, V200%, D100%, D98%, D90%, D50%, D5cc, D2cc, D0.1cc) were assessed. Clinical outcomes and treatment-related complications were analyzed.ResultsA total of 13 patients were included, including 4 patients with prior radiation therapy and 9 without prior radiation therapy; 45 fractions of ISBT were analyzed. Central and non-central pelvic recurrences occurred in 46.2% and 53.8% of patients, respectively. Eight patients received concurrent systemic therapy. The cumulative equivalent dose in 2-Gy fractions (EQD2) to the clinical target volume of recurrence treatment was 64.87 ± 7.16 Gy for patients with prior radiation and 73.03 ± 9.95 Gy for those without prior radiation. The corresponding cumulative EQD2 to the D2cc of the bladder, rectum, and sigmoid colon were 63.98 ± 11.37 Gy vs. 79.00 ± 12.34 Gy, 61.93 ± 8.90 Gy vs. 68.44 ± 9.93 Gy, and 41.22 ± 20.79 Gy vs. 54.49 ± 7.45 Gy, respectively. At a median follow-up of 38 months, 92.3% (12/13) of patients were alive. The 2-year and 3-year local control rates were 92.3% and 82.1%, respectively. Acute Grade 3 toxicity was observed in 30.8%, and late Grade 3 toxicity in 7.7%.ConclusionIndividualized curved-needle ISBT with a 3D-printed applicator provided high-quality treatment for recurrent gynecologic tumors with favorable outcomes and acceptable toxicity.