Offline Adaptive Planning for HDR Brachytherapy in Cervical Cancer
Source: Fu Q, Xu Y, Yang X, et al. Clinical and Translational Radiation Oncology 53 (2025) 100964. Open access, CC BY-NC-ND 4.0.
Background
High-dose-rate (HDR) brachytherapy combined with external beam radiotherapy (EBRT) is the standard of care for locally advanced cervical cancer. Conventionally, each BT fraction is planned independently — which yields locally optimal fractional doses but not necessarily an optimal total dose distribution across the combined regimen.
Method
The authors retrospectively reviewed 9 cervical cancer patients treated with EBRT followed by HDR BT. For each fraction they:
- Used a multi-metric deformable image registration to map and accumulate previously delivered EBRT and BT doses onto the current planning image.
- Imported the accumulated dose distribution as a background dose into a customized commercial BT TPS.
- Re-optimized the current fraction against that background using the dose objectives below.
| Contour | Parameter | Dose (cGy) | Weight | | --- | --- | --- | --- | | HR-CTV | D90 | 600 + background D90 | 100 | | Bladder | Max dose | 450 + max background | 20 | | Rectum | Max dose | 400 + max background | 20 | | Sigmoid | Max dose | 400 + max background | 10 | | Bowel | Max dose | 400 + max background | 10 |
Results
- In ~70% of BT fractions, adaptive BT (ABT) lowered bladder or rectum D2cc versus conventional BT (CBT).
- Mean total-dose reductions with ABT:
- Bladder: D2cc −1.9 ± 2.0 Gy_EQD2, V60 −1.2 ± 1.2%, V50 −0.9 ± 1.1%
- Rectum: D2cc −2.1 ± 1.8 Gy_EQD2, V60 −1.2 ± 1.2%, V50 −1.4 ± 1.3%
- HR-CTV D90 coverage was maintained or slightly improved.
Deformable registration accuracy was validated with mean DSC of 0.92 (bladder), 0.88 (rectum) and 0.94 (uterus + vagina).
Why it matters for procurement
Adaptive BT relies on three practical building blocks: (1) reproducible applicator placement across fractions, (2) MR/CT-compatible applicators that support accurate deformable registration, and (3) a TPS able to optimize against a background accumulated dose. Choosing applicators with stable geometry and clear imaging artifacts directly enables this workflow.
Acknowledgment
The authors acknowledge RL Electronics (Tianjin) for TPS and technical support. Funding: CAMS Innovation Fund for Medical Sciences (2024-I2M-C&T-B-071) and National High Level Hospital Clinical Research Funding.
Published under CC BY-NC-ND 4.0. Full author list and references are available in the downloadable PDF.