3422 - Organ Preservation in Locally Advanced Rectal Cancer Treated with Contact X-Ray Brachytherapy: A Systematic Review and Single-Arm Meta-Analysis

Purpose/Objective(s): This study aimed to perform a meta-analysis of randomized controlled trials (RCTs) and observational studies involving patients with rectal carcinoma treated with (chemo)radiotherapy and a contact x-ray brachytherapy (CXB) boost. The hypothesis is that CXB boost treatment could lead to a high probability of organ preservation and complete or near-complete clinical response.

Materials/Methods: A comprehensive search was conducted across PubMed, Scopus, Cochrane Central, and Web of Science for studies including patients diagnosed with rectal carcinoma and treated with chemo-radiotherapy (EBCRT) and CXB. The primary outcomes were the probability of achieving a complete or near-complete clinical response (cCR/ncCR) and organ preservation. Statistical analysis was performed using OpenMeta[Analyst] software (version 5.26.14). Heterogeneity was assessed using the I² statistic.

Results: Seven studies, comprising 912 patients with rectal carcinoma, were included. A CXB boost was administered to 736 patients (80.7%). Follow-up ranged from 1 to 64.5 months, with a mean follow-up of 41.4 months. The mean age was 71.1 ± 6.72 years, with 63% of patients being male. A CXB dose of <90 Gy was used in 87% of the pooled population. Tumor diameter was <3 cm in 523 patients. CXB boost treatment resulted in a high probability of achieving cCR/ncCR (76.9%; 95% CI: 0.69–0.84; I² = 80.42%) and organ preservation (80.2%; 95% CI: 0.68–0.88; I² = 86.3%), with a low probability of local relapse at 36 months (20.2%; 95% CI: 0.17–0.23; I² = 0%). Late grade 3 rectal bleeding occurred in four out of 635 patients (0.1%; 95% CI: 0.004–0.023; I² = 0%). Functional outcomes, measured using the Low Anterior Resection Syndrome (LARS) score, demonstrated a nearly 40% probability of achieving a score below 30 points (38.2%; 95% CI: 0.07–0.83; I² = 94.8%).

Conclusion: This meta-analysis, including 736 patients from seven studies, provides evidence supporting the efficacy and safety of CXB boost in rectal cancer, with a high probability of organ preservation and cCR/ncCR and no significant late adverse events. However, further high-quality, large-scale randomized controlled trials are needed to confirm these findings.