In the present patient, the disappearance of both tumor vessels and a tumor stain from the right gastric artery and the common trunk of the left gastric and the left hepatic arteries, for which no embolization was performed, was observed within a few hours after hemostatic radiotherapy. Furthermore, physical findings and laboratory data indicated an immediate hemostatic effect. These findings suggest that hemostatic radiotherapy may have contributed to the rapid disappearance of tumor vessels.

The hemostatic mechanism of radiotherapy for gastric cancer bleeding remains not clearly understood. Previous studies have hypothesized several potential mechanisms, including changes in tumor vessels, radiation-induced platelet aggregation, tumor shrinkage, and fibrosis of the tumor and surrounding tissues [6,7,8,9]. However, to the best of our knowledge, no reports have clearly demonstrated the mechanism of hemostatic radiotherapy in vivo. Conventional radiotherapy with 1.8–3.0 Gy per fraction causes genetic damage to irradiated cells, leading to tumor shrinkage, and fibrosis of the tumor and surrounding tissues for a few days to months. In contrast, hypofractionated radiotherapy with a high dose per fraction can directly cause vascular changes in tumor vessels by damaging vascular endothelial cells within a few hours to days, mildly at 5–10 Gy per fraction and severely at 10 Gy or more per fraction [10, 11]. Therefore, a higher radiation dose per fraction can cause a significantly stronger and earlier impact on tumor vessels directly. However, a radiation dose per fraction cannot be increased without an upper limit because a higher radiation dose per fraction also causes more severe damage to normal tissues and organs. The frequently used radiotherapy regimens in a multicenter prospective study of hemostatic radiotherapy for gastric cancer conducted in Japan were 8 Gy in a single fraction, 20 Gy in 5 fractions (4 Gy per fraction), and 30 Gy in 10 fractions (3 Gy per fraction) [5]. Therefore, 8 Gy in a single fraction, which is also used in the present patient, is considered a safe upper dose at present when hemostatic radiotherapy for gastric cancer is performed with a higher dose in a single fraction. The angiographic images obtained in the present patient may indicate that the disappearance of tumor vessels and the tumor stain occurred within a few hours after radiotherapy, suggesting a possible association with the hemostatic effect of radiotherapy.

The immediate effects of hemostatic radiotherapy for gastric cancer bleeding have not been extensively researched. In the case of painful bone metastases, where palliative radiotherapy is often employed, the median time from radiotherapy to the onset of pain relief is reported to be 2–4 weeks [12, 13]. Therefore, many clinicians may assume that hemostatic radiotherapy also requires a similar timeframe to take effect. To date, two prospective studies have investigated hemostatic radiotherapy for gastric cancer bleeding, with initial evaluations conducted 2–4 weeks after treatment [3, 5]. Consequently, no prospective data is available on its hemostatic effects in the early phase after radiotherapy. However, a retrospective analysis showed that hemostasis was achieved at a median of 2 days, with some patients experiencing hemostatic effects as early as the following day after radiotherapy [14]. In this present case, hemostasis was achieved on the same day of radiotherapy, and this fact was consistent with the observed changes of tumor vessels and tumor stain in the angiography after hemostatic radiotherapy. This suggests that bleeding control can be achieved immediately in some patients following radiotherapy. Therefore, emergency radiotherapy should be considered a life-saving option for patients with severe gastric cancer bleeding when other local hemostatic treatments are not feasible.

In conclusion, we reported a case of gastric cancer bleeding in which both tumor vessels and the tumor stain disappeared, and an immediate hemostatic effect was achieved shortly after hemostatic radiotherapy followed by TAE. Our findings suggest that the hemostatic mechanism of radiotherapy is related to early changes of tumor vessels and tumor stains. Given that some patients, including those in our case and previous studies, can achieve immediate hemostasis, hemostatic radiotherapy should be considered a viable emergency treatment option for gastric cancer bleeding.