ESTRO meets Asia 2024 - Abstract Book

S205

Interdisciplinary – Lower GI

ESTRO meets Asia 2024

254

Proffered Paper

preventive effect of bifidobacterium longum on radiation-induced intestinal injury: a phase 2 trial

yinyin yang, shang cai, ye tian

Department of Radiotherapy and Oncology, he Second Affiliated Hospital of Soochow University, suzhou, China

Purpose/Objective:

Acute radiation-induced intestinal injury (ARIII) is a common side-effect of abdominal and pelvic radiotherapy and is detrimental to both prognosis and quality of life of cancer patients. This study aimed to assess the effect of supplementing Bifidobacterium longum BL21 (referred to as BL21) in preventing ARIII, as well as the impact on compositions of intestinal microbiota and metabolites.

Material/Methods:

This single-center, open-label, single-arm, phase II trial (registration number: ChiCTR2300069881) included patients with cervical cancer, endometrial cancer, or rectal cancer who underwent radical or adjuvant radiotherapy with or without chemotherapy. All eligible patients are instructed to take 1 packet of BL21 bacterial powder (containing 20 billion CFU of BL21) orally daily, throughout the course of external beam radiotherapy. Weekly follow-ups were conducted during radiotherapy, with the primary endpoint being the incidence of grade ≥2ARIII, as assessed by the Radiation Therapy Oncology Group (RTOG) criteria. Furthermore, Stool samples were collected from patients at the start and end of radiotherapy, respectively. The composition of intestinal microbiota in the samples was analyzed using 16S rRNA sequencing. Additionally, untargeted GC-MS and LC-MS were employed to analyze fecal metabolites.

Results:

From April 7, 2023, to October 31, 2023, a total of 44 patients were enrolled. The overall incidence of ARIII was 84.1%, with only 27.2% experiencing grade ≥2 ARIII, significantly lower than the reported 65% in historical control groups. No adverse events related to BL21 were reported in any patients. Regarding intestinal microbiota, the α diversity of intestinal microbiota significantly decreased after radiotherapy and was associated with the severity of ARIII, while no significant differences were observed in β-diversity. The ratio of Firmicutes/Bacteroidetes increased after radiotherapy, and the abundance of Lachnospiraceae significantly increased after radiotherapy (P=0.025). In terms of metabolites, patients experiencing grade 0/1 ARIII had different metabolites detected in their fecal samples at the end of radiotherapy, including various metabolites from short-chain fatty acid and tryptophan metabolic pathways, such as alanine, valine, isoleucine, and indole-3-acetic acid. Conversely, patients experiencing grade ≥2 ARIII did not have any differential metabolites detected related to these pathways.

Conclusion:

Prophylactic use of BL21 can prevent grade ≥2 ARIII, making it a safe, simple, and effective method in clinical practice. The potential mechanism underlying the protective effect of BL21 may relate to the resconstruction of intestinal microbiota, leading to an increase in beneficial bacteria that promote the production of short-chain fatty acids and activate the tryptophan metabolism pathway.