Can Deformable Image Registration Improve Cumulative Dose Assessment and Enable Safer Dose Escalation in Rectal Cancer Radiotherapy? A Retrospective Cohort Study
| Author | Mehdi Eslamizadeh | en |
| Author | Mohamad Dosaranian-Moghadam | en |
| Author | Seyed Vahab Shojadini | en |
| Author | Somayeh Raeis Dana | en |
| Issued Date | 2026-12-31 | en |
| Abstract | Background: Accurate cumulative dose assessment is essential in patients with rectal cancer undergoing fractionated high-dose-rate (HDR) brachytherapy, particularly when the external beam radiation therapy (EBRT) dose is incorporated. Objectives: This study aimed to evaluate the dosimetric impact of deformable image registration (DIR) on cumulative dose assessment in patients with rectal cancer undergoing fractionated high-dose-rate (HDR) brachytherapy. Methods: In this retrospective cohort study, 12 patients with locally advanced rectal cancer were treated with EBRT (50.4 Gy in 28 fractions) followed by HDR brachytherapy (4 fractions of 6 - 7 Gy). DIR-based dose accumulation was performed across all brachytherapy fractions using MIM software, with conversion to the equivalent dose in 2 Gy fractions (EQD2) and voxel-wise summation. The EBRT dose distribution was rigidly registered to the final brachytherapy computed tomography (CT) scan to calculate the total dose. Dose-volume parameters, including D90 for the clinical target volume (CTV) and D2cc, D1cc, and D0.1cc for organs at risk (OARs), were compared between DIR-based and conventional dose summation. Registration quality was evaluated using the Dice similarity coefficient (DSC). Results: DIR resulted in significant reductions in cumulative OAR doses compared with simple summation, including rectum D2cc (−2.5 ± 1.2 Gy, P < 0.01) and bladder D2cc (−1.9 ± 1.0 Gy, P = 0.02), as well as a modest increase in target coverage (CTV D90: +1.3 ± 1.1 Gy, P = 0.03). The median D90 improvement after DIR-based re-optimization was 1.77 Gy EQD2. DIR quality was acceptable for most structures (DSC > 0.80), although it was lower for the CTV (0.73) owing to its irregular shape and sensitivity to motion. Conclusions: DIR improves the accuracy of cumulative dose assessment in rectal cancer radiotherapy and may facilitate safer dose escalation and improved organ sparing. Integrating DIR into adaptive brachytherapy workflows offers a promising strategy for personalized treatment in anatomically variable pelvic regions. | en |
| DOI | https://doi.org/10.5812/ijcm-168776 | en |
| URI | https://brieflands.com/journals/ijcm/articles/168776 | en |
| Keyword | Deformable Image Registration | en |
| Keyword | Dose Accumulation | en |
| Keyword | Equivalent Dose In 2 Gy Fractions | en |
| Keyword | Brachytherapy | en |
| Keyword | Rectal Cancer | en |
| Keyword | Dose-volume Histogram | en |
| Keyword | TG-43 | en |
| Publisher | Brieflands | en |
| Title | Can Deformable Image Registration Improve Cumulative Dose Assessment and Enable Safer Dose Escalation in Rectal Cancer Radiotherapy? A Retrospective Cohort Study | en |
| Type | Research Article | en |
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