253P - Hemostatic radiotherapy for gastric cancer: MRI as an alternative to endoscopy for post-treatment evaluation

Background

Pretreatment diagnosis by diffusion-weighted magnetic resonance imaging (DW-MRI) is useful to determine the effect of chemotherapy for gastric cancer. Here, we investigated the relationship among DW-MRI, endoscopy, and tumor markers.

Methods

Eight patients underwent hemostatic radiotherapy (RT) for gastric cancer in this prospective study from 2019 to 2021. The patients completed MRI, endoscopy, and blood tests before RT; MRI, endoscopy, and blood tests 1 month after RT; and MRI and blood tests 3 months after RT. Correlations between changes in apparent diffusion coefficient (ADC) derived from DW-MRI and the tumor marker carcinoembryonic antigen (CEA) were investigated.

Results

Univariate analysis of overall survival showed that sex and chemotherapy treatment were statistically significant factors. The CEA values before and 1 month after RT decreased significantly. There was no statistical difference between the CEA value 1 and 3 months after RT. The ADC value before and 1 month after RT increased significantly but not between 1 and 3 months after RT. Comparing the ratio of ADC before RT to 1 (or 3) month(s) after RT with that of CEA before RT to 1 (or 3) month(s) after RT, we found an inverse relationship between the two ratios.

Conclusions

The usefulness of DW-MRI has been reported mainly for solid tumors. Herein, we evaluated the usefulness of DW-MRI for gastric cancer using a tumor marker in RT settings. We showed that changes in the ADC values and changes in the CEA values are correlated using ratios (before/1 or 3 months after RT). Additionally, 3 months after treatment, a decrease in ADC appeared earlier than a decrease in CEA. Our findings suggest that ADC may represent biological changes earlier than CEA.

Clinical trial identification

CTR-UMIN000026362.

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.