Regional Difference of Liver Cancer in Japan: A Real-world Evidence Using the National Database of Health Insurance Claims

Background The etiology of liver cancer is changing to metabolic dysfunction-associated steatotic liver disease, and ultrasound elastography is useful for identifying high-risk patients. However, these regional differences remain unclear. We aimed to investigate regional differences in the prevalence of liver cancer and the use of ultrasound elastography in Japan using the National Database of Health Insurance Claims (NDB). Methods We used NDB open data from 2020. The standardized claims data ratio (SCR) was used to evaluate regional differences. We investigated medical receipt information for liver cancer, diabetes-related diseases, and elastography in 47 prefectures. Results The highest SCR for liver cancer was observed in Kyushu (median 134, IQR [109-139]), followed by Chugoku (113, [110-132]), Kinki (109, [89-126]), and Shikoku (107, [100-121]), highlighting a significant concentration in Western Japan (The mean SCR; 114.9 in Western Japan, 88.5 in Eastern Japan: p<0.0001). A higher SCR has also been observed in the treatment of liver cancer, including hepatic resection and radiofrequency ablation, in Western Japan. Similarly, in Western Japan, higher SCRs have also been observed for diabetes-related diseases, such as glucose intolerance, ischemic cardiovascular disease, angina pectoris, and ischemic cerebrovascular disease. However, the SCR for transient elastography and shear wave elastography is low in many prefectures throughout Japan. Conclusion The morbidity of liver cancer and diabetes-related diseases is higher in Western Japan. However, ultrasound elastography is not widely used in Japan. There is an urgent need to promote awareness of ultrasound elastography to screen patients at high risk for liver cancer, particularly in Western Japan.