The effect of dose escalation on gastric toxicity when treating lower oesophageal tumours: a radiobiological investigation

Radiotherapy-Induced Digestive Injury: Diagnosis, Treatment and Mechanisms

Radiotherapy is one of the main therapeutic methods for treating cancer. The digestive system consists of the gastrointestinal tract and the accessory organs of digestion (the tongue, salivary glands, pancreas, liver and gallbladder). The digestive system is easily impaired during radiotherapy, especially in thoracic and abdominal radiotherapy. In this review, we introduce the physical classification, basic pathogenesis, clinical characteristics, predictive/diagnostic factors, and possible treatment targets of radiotherapy-induced digestive injury. Radiotherapy-induced digestive injury complies with the dose-volume effect and has a radiation-based organ correlation. Computed tomography (CT), MRI (magnetic resonance imaging), ultrasound (US) and endoscopy can help diagnose and evaluate the radiation-induced lesion level. The latest treatment approaches include improvement in radiotherapy (such as shielding, hydrogel spacers and dose distribution), stem cell transplantation and drug administration. Gut microbiota modulation may become a novel approach to relieving radiogenic gastrointestinal syndrome. Finally, we summarized the possible mechanisms involved in treatment, but they remain varied. Radionuclide-labeled targeting molecules (RLTMs) are promising for more precise radiotherapy. These advances contribute to our understanding of the assessment and treatment of radiation-induced digestive injury.

mRNA and lncRNA Expression Profiling of Radiation-Induced Gastric Injury Reveals Potential Radiation-Responsive Transcription Factors

Radiation-induced gastric injury is a serious concern that may limit the duration and the delivered dose of radiation. However, the genome-wide molecular changes in stomach upon ionizing radiation have not been reported. In this study, mouse stomach was irradiated with 6 or 12 Gy X-ray irradiation and we found that radiation resulted in the atrophy of gastric mucosa and abnormal morphology of chief and parietal cells. Radiation-induced gastric injury was accompanied by an increase in the serum levels of pepsinogen A and pepsinogen C but not gastrin-17. The expression profiles of messenger RNA (mRNA) and long noncoding RNA (lncRNA) in normal and irradiated gastric tissues were measured by microarray analysis. Results revealed 17 upregulated and 10 downregulated mRNAs were consistent in 6 and 12 Gy irradiated gastric tissues, including D site-binding protein (Dbp) and fibrinogen-like protein 1 (Fgl1). Thirteen upregulated and 96 downregulated lncRNAs were commonly changed in 6 and 12 Gy irradiated gastric tissues. The dysregulated mRNAs were implicated in multiple pathways and showed coexpression with lncRNAs. To identify motifs for transcription factors and coactivators in the proximal promoter regions of the dysregulated RNAs, the bioinformatic tool Biopython was used. A variety of common motifs that are associated with transcription factors were identified, including ZNF263, LMX1B, and Dlx1. Our findings illustrate the molecular changes during radiation-induced gastric injury and the potential transcription factors driving this alteration.

Intrafractional dose variation and beam configuration in carbon ion radiotherapy for esophageal cancer

Background

In carbon ion radiotherapy (CIR) for esophageal cancer, organ and target motion is a major challenge for treatment planning due to potential range deviations. This study intends to analyze the impact of intrafractional variations on dosimetric parameters and to identify favourable settings for robust treatment plans.

Methods

We contoured esophageal boost volumes in different organ localizations for four patients and calculated CIR-plans with 13 different beam geometries on a free-breathing CT. Forward calculation of these plans was performed on 4D-CT datasets representing seven different phases of the breathing cycle. Plan quality was assessed for each patient and beam configuration.

Results

Target volume coverage was adequate for all settings in the baseline CIR-plans (V₉₅ > 98% for two-beam geometries, > 94% for one-beam geometries), but reduced on 4D-CT plans (V₉₅ range 50–95%). Sparing of the organs at risk (OAR) was adequate, but range deviations during the breathing cycle partly caused critical, maximum doses to spinal cord up to 3.5x higher than expected. There was at least one beam configuration for each patient with appropriate plan quality.

Conclusions

Despite intrafractional motion, CIR for esophageal cancer is possible with robust treatment plans when an individually optimized beam setup is selected depending on tumor size and localization.