ESTRO 2024 - Abstract Book

S254

Brachytherapy - Gynaecology

ESTRO 2024

[2] Recommendations from gynaecological (GYN) GEC ESTRO working group (II): concepts and terms in 3D image based treatment planning in cervix cancer brachytherapy-3D dose volume parameters and aspects of 3D image based anatomy, radiation physics, radiobiology, Richard Pötter, Christine Haie-Meder, Erik Van Limbergen, Radiother Oncol. 2006 Jan;78(1):67-77

[3] MRI-guided adaptive brachytherapy in locally advanced cervical cancer (EMBRACE-I): a multicentre prospective cohort study, Richard Pötter, Kari Tanderup, Maximilian Paul Schmid, et al. Lancet Oncol 2021; 22: 538–47

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Digital Poster

Do vaginal dose points reflect vaginal Dose-Volume parameters in Cervical cancer Brachytherapy?

Nikhila Radhakrishna 1 , Naveen Thimmaiah 1 , Hamsini Rayas 1 , Tanvir Pasha 1 , Siddanna Palled 1 , Rekha Reddy Bucchapudi 2 , Nithin Bhaskar 1 , Lokesh Vishwanath 1 1 Kidwai Memorial Institute of Oncology, Radiation Oncology, Bangalore, India. 2 Kidwai Memorial Institute of Oncology, Radiation Physics, Bangalore, India

Purpose/Objective:

Vagina is an Organ at risk(OAR) as well as a component of the target in its upper part in Cervical Brachytherapy. While the dose effect relationship has been difficult to determine in the high dose gradient upper vaginal areas, the intermediate dose and low dose regions of the vagina remain under-evaluated (1,2). Dose points have been recommended within the vagina by Westervald et al(3). Whether 2-D dose points selected within the vaginal cavity can represent the spatial doses received by the distensible walls of the vagina remains a question yet to be answered(4). The current study intends to identify whether there is any correlation between the Dose Volume (DV) parameters of the vagina with the corresponding recommended vaginal dose points.

Material/Methods:

Records of cervical cancer patients between July 2019 to March 2020 were selected. External Beam Radiotherapy (EBRT) of 45-50 Gy/25 fractions was delivered by 3 Dimensional Conformal technique. Patients with initial involvement of lower third vagina were excluded. ICBT procedure was performed using the Manchester applicator. A dose of 6.5 Gy x 4 fractions was prescribed to Point A. The plans were further optimised manually to obtain optimal doses to target and OARs. The vaginal walls were retrospectively contoured. Upper vagina corresponding to the region between cervical external os and urethra-vesical junction (UV junction); mid vagina between the UV junction and the Posterior inferior border of symphysis pubis (PIBS) point; lower vagina between PIBS point up to the introitus (5). The wall extraction method was adopted for uniform contouring of the vagina with a thickness of 3 mm, followed by manual editing of the vaginal anatomical boundaries. The DV parameters of the vagina were documented. Vaginal dose points were positioned as per recommendations by Westervald et al (3) . The PIBS point is considered as the zone of transition from mid vagina to lower vagina. It was placed at the intersection of the tandem and the plane passing through the posterior inferior border of symphysis pubis. The two other points plotted were the PIBS + 2 cm which is superior to PIBS point and PIBS – 2 cm which is inferior to PIBS point.