ESTRO 2024 - Abstract Book

S276

Brachytherapy - Gynaecology

ESTRO 2024

Jürgenliemk-Schulz, Kari Tanderup, Christian Kirisits, and Richard Pötter. “Prognostic Implications of uterine cervical cancer regression during chemoradiation evaluated by the T-Score in the multicenter EMBRACE I Study”. International Journal of Radiation Oncology Biology Physics. Volume 113, Number 2, 2022.

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Digital Poster

A hybrid IGBT technique for cervical cancer in an outpatient setting: Experience at the NCIS

Syadwa Abdul Shukor, Yiat Horng Leong, Michelle Tseng, Vicky Koh

National University Cancer Institute Singapore, Radiation Oncology, Singapore, Singapore

Purpose/Objective:

To report planning and clinical outcome in locally advanced cervical cancer (LACC) using CT-based hybrid image guided brachytherapy (IGBT) in an outpatient setting

Material/Methods:

Between 2014 and 2022, 171 women with International Federation of Gynecology and Obstetrics (FIGO) stage IB to IVA cervical carcinoma treated with definitive external beam radiation therapy (EBRT) of 45 Gy to 50.4 Gy in 1.8 Gy daily fractions given over 25 to 28 fractions with 10 MV photons, 5 days a week, followed by brachytherapy (BT), were retrospectively reviewed. In patients receiving additional EBRT boost to pelvic or para-aortic lymph nodes (LN), the boost therapy ranges from 56 Gy to 56 Gy to 59.4 Gy. Conventional 3D conformal or intensity modulated radiation therapy (IMRT) was utilised in our patients as indicated. Patients who had no follow-up contact after the last treatment and were not using the hybrid IGBT technique were excluded. High-dose rate (HDR) IGBT was administered in 6–8Gy per fraction over 3-5 insertions via CT/MR compatible applicators (Fletcher, Utrecht, Venezia, or Geneva) utilising an 192Ir after-loader high-dose rate system. Applicator insertions were performed in an outpatient setting with the use of a narcotic and anxiolytic regimen as moderate to deep sedation with paracervical block. Pre-brachytherapy MRI was utilised to assess the treatment response to EBRT and to guide hybrid IGBT planning. At each implantation, all patients had a urinary catheter in situ and received a bowel enema before undergoing a planned CT simulation. Delineation of target volumes, high-risk and intermediate-risk clinical target volume (HR CTV and IR-CTV), as well as organs at risk (OARs), including the bladder, rectum, and sigmoid, was performed according to the GEC-ESTRO recommendations. Dose and target coverage were adapted to D90 HR-CTV (D90: minimal dose to 90% of clinical target volume). The planning aims were ≥ 80 Gy to D90 HR-CTV (dose in 2 Gy equivalents: EQD2, summing EBRT and BT, and applying a linear quadratic model with an α/β ratio of 10 Gy and a half-time repair of 1.5 h). Dose constraints were < 70 Gy to maximally 2 cm3 exposed areas of the rectum, < 65 Gy to maximally 2 cm3 exposed areas of the sigmoid colon (D2cm3), and 80 Gy to D2cm3 of the bladder (EQD2, similar model with an α/β of 3Gy). Optimisation was performed manually later to adapt dwell times to the topography of the implant. The dose was prescribed at a D90 HR-CTV volume. Patients were evaluated at 12 weeks with imaging (MRI pelvis, CT Abdo/Pelvis, or PET CT) and clinical examination. Toxicities were recorded using the National Cancer Institute Common Terminology Criteria for Adverse Events version 5.0.

Results: