Session Item

To undertake a dosimetric plan quality review for locally advanced cervical cancer high dose rate brachytherapy treated using modern evidence-based planning aims from data published since the advent of MRI guided brachytherapy for cervix cancer. 

Patients were treated with curative intent chemoradiotherapy followed by a brachytherapy boost. Planning aims were based on the EMBRACE II trial protocol [1] and more recent publications [2]. The brachytherapy boost was delivered in three fractions. Interstitial needles were available when clinically indicated. All patients were planned using MR guidance, with both volume and graphical optimization tools available. Since this institution implemented modern evidence-based planning aims, a change in brachytherapy systems was also undertaken, including change in applicator design. The applicator in the first system was the Fletcher-Suite-Delclos applicator, with or without interstitial components. In the second system, the Advanced Gynaecology Applicator (Venezia) was available, together with parallel and oblique needles and vaginal caps. Dose volume histogram parameters, point doses, TRAK, from treatment plans were retrospectively collected. Changes in plan quality measures over time are reported. All doses are reported as EQD2, combined with EBRT.  

61 patients were treated since the implementation of modern evidence-based planning aims.  The mean CTV-HR dose for the first system was 92Gy, and 90.9Gy for the second system. The average bladder D2cc decreased from 78.6Gy to 73.9Gy, average rectum D2cc decreased from 61.0Gy to 59.8Gy and average sigmoid decreased from 60.3Gy to 57.2Gy. 80.3% of patients had a CTV_HR dose >90Gy.  88.1% of patients had a Bladder D2cc <90Gy. 90% of patients had a Rectum D2cc <75Gy.  All patients met the planning limit for the sigmoid.  TRAK decreased with new brachytherapy system. 

This demonstrates that evidence based IGABT planning aims can be delivered using the two major brachytherapy commercial systems. Applicator choice makes a difference to the treatment plan quality parameters. 

References:

1. Pötter R, Tanderup K, Kirisits C etal. The EMBRACE II Study: The Outcome and Prospect of Two Decades of Evolution within the GEC-ESTRO GYN Working Group and the EMBRACE Studies. Clinical and Translational Radiation Oncology 2018;9:48–60.

2. Tanderup, K, Nesvacil N, Kirchheiner K etal. Evidence-Based Dose Planning Aims and Dose Prescription in Image-Guided Brachytherapy Combined With Radiochemotherapy in Locally Advanced Cervical Cancer.  Seminars in Radiation Oncology 2020;30 (4):311–27.