S25
Brachytherapy - Gastro-intestinal, paediatric brachytherapy, miscellaneous
ESTRO 2026
dose rate
Mini-Oral 3453
Contact X - ray vs Endorectal HDR Brachytherapy as a Boost in Rectal Cancer: A Systematic Review and Meta - analysis of Prospective Trials Teng Hwee Tan, Francis Ho, Jeremy Tey, Balamurugan A Vellayappan, Cheng Nang Leong, Elizabeth Chuk, Syadwa Binti Abdul Shukor, Yu Yang Soon Radiation Oncology, National University Cancer Institute Singapore, Singapore, Singapore Purpose/Objective: Organ preservation (OP) strategies for non - metastatic rectal cancer increasingly rely on effective non - surgical treatments. In addition to standard external beam radiotherapy (EBRT), brachytherapy boost can be delivered as contact X - ray (CXB) or endorectal high - dose - rate brachytherapy (HDRBT). These modalities are often conflated in the literature, obscuring their respective roles in OP. Material/Methods: We conducted a systematic review and meta - analysis of prospective studies of localized, non - metastatic rectal cancer treated with EBRT plus a CXB or HDRBT boost. MEDLINE and Embase were searched for publications from 2000–2025. The primary outcomes were clinical complete response (cCR) and OP. Proportions were pooled using fixed - effects meta - analysis with logit transformation. Trial - level meta - regression explored predictors including T - stage distribution and tumour height. Results: Nine prospective trials with a total of 448 participants met inclusion criteria. Pooled cCR was higher with CXB than HDRBT (76% [95% CI, 69–82%] vs 34% [95% CI, 28–40%]; test for subgroup differences p<0.01), as was OP (65% [95% CI, 58–72%] vs 19% [95% CI, 14–25%]; p<0.01). A higher proportion of T3–T4 disease predicted lower cCR (p=0.0032) and lower OP (p=0.0007), whereas tumour height 0–6 cm from the anal verge did not predict cCR (p=0.310) or OP (p=0.105). Local recurrence did not differ significantly between CXB and HDRBT (12% [95% CI, 8–18%] vs 13% [95% CI, 9–18%]; p=0.74). Rates of grade 2–3 proctitis were similar (p=0.10) and grade 3 proctitis showed no significant difference (p=0.07). Grade 3 rectal bleeding was lower with CXB (3% [95% CI, 1–7%] vs 13% [95% CI, 4–28%]; p=0.01). Conclusion: Across prospective trials, CXB boost was associated with higher cCR and OP than HDRBT. However, between trial differences, particularly a greater burden of T3–T4 disease, likely confound these effects, emphasizing the need for randomized or carefully matched comparative studies to define optimal selection and sequencing for OP. Keywords: organ preservation, contact x-ray, high
Digital Poster 3963
Rectal cancer HDR brachytherapy: MAASTRO rectal applicator treatment planning and commissioning Robert Voncken 1 , Evert Limbergen van 1 , Gabriel Fonseca 1 , Jan E Palmgren 1 , Britt Hupkens 1 , Murillo Bellezzo 1 , Celine Beveren van 1 , Erik Roelofs 1 , Brigitte Reniers 2 , Frank Verhaegen 1 , Maaike Berbée 1 1 Department of Radiation Oncology (Maastro), GROW Research Institute for Oncology and Reproduction, GROW Research Institute for Oncology and Reproduction, Maastricht, Netherlands. 2 Research group NuTeC, Centre for Environmental Sciences, Hasselt University, Diepenbeek, Belgium Purpose/Objective: Organ preservation in rectal cancer is increasingly pursued to avoid major surgery and the need for a stoma. The OPERA trial demonstrated that dose escalation using contact X-ray brachytherapy (CXB) significantly improved rectal preservation without compromising oncologic outcomes (1). However, CXB requires a dedicated 50 kV Papillon system, limiting accessibility. In collaboration with Varian we developed the MAASTRO Rectal Applicator (MRA) - available in two diameters- to enable similar dose escalation using HDR 192Ir sources and existing Varian afterloaders.The goal of this work is to provide the clinical treatment plans for the applicators, which were used in the clinical feasibility trial, and to provide a practical methodology for the commissioning of these applicators. Material/Methods: Standard treatment plans replicating CXB 3x30 Gy treatments, with a 50 kV dose depth profile, were created using BrachyVision. These plans were optimized with Varian’s Acuros algorithm (dose-to- water), accounting for tungsten shielding.Gafchromic films were used for both verification of the source channel and dosimetry of the clinical plans, employing custom made applicator holders and a 20 × 20 × 20 cm phantom. The source trajectories were verified over 3 cm from the distal end in 1 cm steps. The film measurements were compared to the source positions from the TPS. Dosimetry for the clinical plans was performed with the applicator centered in the phantom. EBT-XD film was placed at a distance of 2mm from the applicator surface to validate the delivery dose. Films were analyzed with FilmQA Pro. Results: Standard treatment plans were normalized to 23.1 Gy at 2 mm (2), considering dose homogeneity at this depth, to create plans with a 30 Gy surface dose and the 95% isodose covering the predefined high dose
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