Christopher J. Tien

Interstitial cervical needle-guide ring-cap prototype for patient-specific ring-and-tandem brachytherapy

We have developed a unique cap that could be paired with our existing commercially-available MRI-compatible ring-and-tandem applicator (R&T) that can provide a patient-specific cervical needle guide for hybrid intracavitary-interstitial brachytherapy (IC/ISBT). Prototype guide caps with six channels for interstitial needles were rendered in SolidWorks (Dassault Systèmes SE, Vélizy-Villacoublay, France), coupled with Mick Radio-Nuclear Instruments (Mt Vernon, NY, USA) R&T. Prototypes were printed using Formlabs 3B printers and Gray Resin (Formlabs, Somerville, MA, USA). Achievable bend radii for interstitial needles were determined using custom jigs. A pilot cohort of previously-treated IC/ISBT patients was replanned with virtual needle paths reconstructed in EclipseBV (Varian Medical Systems, Palo Alto, CA, USA). Physical design constraints (bend radius, position) were used to determine the impact on EQD Software-rendered guide caps prototypes were 3D-printed and tested to all be physically compatible with our existing commercially-available R&T. The channels physically accommodated six interstitial needles with bending precision ±1°. Among the cohort, the HR-CTV D We have designed and produced a guide cap prototype that can be used to improve our existing commercially-available R&T with IC/ISBT capabilities for customizable angles and positions. The guide caps have been shown to enhance dosimetry and can be used for patient-specific treatment.

Clinical outcomes following brachytherapy for endometrial cancer patients with narrow vaginal anatomy.

Adjuvant high-dose-rate (HDR) vaginal brachytherapy (VBT) for endometrial cancer (EC) is delivered with vaginal cylinders ranging from 2.0 to 4.0 cm in diameter. Dose heterogeneities as high as 170-210% can be observed with the narrowest 2.0 cm cylinders potentially increasing the risk of vaginal scarring. Therefore, use of larger diameter cylinders is favored when clinically feasible. Nonetheless, certain clinical scenarios necessitate the use of narrow cylinders despite their unfavorable dosimetry. This study reports the clinical outcomes of EC patients treated with 2.0 cm diameter cylinders at a single institution. From an IRB-approved database of 770 EC patients treated with VBT (11/2015-07/2024), 45 (5.8%) treated with 2.0 cm diameter cylinders were retrospectively reviewed. All received 10 Gy x 3 fractions prescribed to the cylinder surface, to mitigate high surface doses. Patient demographics, recurrence rates, and toxicities were analyzed. Toxicities were assessed using CTCAE v4.0, and freedom from vaginal recurrence was determined by Kaplan-Meier analysis. The median age was 69 years, and 80% were nulliparous. Most had stage I-II disease (82%), and the most common histology was endometrioid (69%). The 2-year freedom from vaginal recurrence was 97% with only 1 in-field recurrence. No grade ≥2 gastrointestinal or urinary toxicities were observed. Freedom from grade ≥2 vaginal stenosis was 85%. Use of the 2.0 cm diameter cylinder was rare and used in <6% of EC patients treated with VBT. The regimen of 10 Gy x 3 fractions to the cylinder surface was well-tolerated and achieved excellent local control.