Emily Flower

Evaluation of plan quality, safety, and toxicity of brachytherapy for locally advanced cervical cancer in an Australian setting following changes in prescription and applicator design

AbstractIntroductionChemoradiotherapy with MRI‐guided brachytherapy boosts is the standard of care for locally advanced cervical cancer. Data from the RetroEMBRACE and EMBRACE I trials provide dose‐response curves for target volumes and OAR. This study evaluated plan quality, safety and toxicity following escalation of the CTV_HR D90 prescription from 80–90 Gy to 85–95 Gy for two different applicator designs.MethodsA retrospective dosimetric plan quality review was undertaken for consecutively treated locally advanced cervical cancer brachytherapy boosts between 2017 and 2022, and the relationships between implant total reference air kerma (TRAK), CTV_HR volume and vaginal dose were investigated. Safety and ≤grade 3 toxicity results were evaluated.ResultsSeventy patients were identified. All patients received a CTV_HR D90 dose >85 Gy and rectum D2cm3 of <75 Gy, while 88.6% of patients received a bladder D2cm3 <90 Gy. Needles were used in 48.6% of patients, and the mean percentage needle TRAK was 38.2%. Increasing the percentage of needle TRAK decreased vaginal TRAK. Sixty‐three patients had more than 12 months of follow‐up (median 27 months). From this cohort, grade 3 or higher toxicity for vaginal, genitourinary, gastrointestinal and fistula events were seen in 3.2%, 1.6%, 0% and 3.2% of patients, respectively.ConclusionIncreased dose prescriptions and a change of applicator design were successfully adopted into an Australian practice. Applicator design and interstitial needle use affect the plan quality and ability to meet OAR dose constraints following target dose escalation. No safety concerns with needle use or dose escalation were identified.

Improving plan quality in cervical brachytherapy using a simple knowledge-based prediction tool for OAR dose (D2cm3)

Toxicity from cervical brachytherapy has been demonstrated to correlate with the D2cm The overlap volume histogram (OVH) method was used to determine the distance for 2cm Mean bladder D2cm A simplified knowledge-based planning method was used to predict D2cm

Improving plan quality in cervical cancer brachytherapy using knowledge-based planning for direction modulated brachytherapy tandem applicator

The bladder and rectal toxicities in cervical cancer brachytherapy are positively correlated with the DVH parameter: D2cc. This study evaluates the feasibility of knowledge-based planning to predict the D2cc, identify suboptimal plans, and improve the plan quality with Direction Modulated Brachytherapy (DMBT) applicators using knowledge-based planning based on linear relationship between overlap distances and D2cc. The overlap volume histogram (OVH) method was used to determine the distances for 2 cm The mean bladder D2cc decreased by 4.3% and 10.3% for conventional applicators, and 4.4% and 3.6% for DMBT applicators for Models 1 and 2, respectively. The rectum D2cc decreased by 3.4% and 10.7% for conventional and 3.0% and 5.0% for DMBT applicators, respectively. The sigmoid D2cc decreased by 3.1% and 6.9% for conventional and 3.2% and 5.9% for DMBT applicators, respectively. There were also significant reductions for the recto-vaginal (RV-RP) point and posterior-inferior border of symphysis (PIBS) reference points: PIBS+2cm, PIBS+1cm, PIBS-1cm, and PIBS-2cm, for both models as well. A knowledge-based planning method successfully predicted D2cc and optimized brachytherapy plans for cervical cancer. The proposed model demonstrates the feasibility of predicting D2cc, detecting suboptimal plans, and improving the plan quality especially for DMBT where cumulative clinical experience is limited.