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. 2025 Jan 22;66(1):82-88.
doi: 10.1093/jrr/rrae100.

Utilization and regional disparities of radiotherapy in cancer treatment in Japan: a longitudinal study using NDB open data

Kazuya Takeda  1   2 , Rei Umezawa  1 , Takaya Yamamoto  1 , Noriyoshi Takahashi  1 , Hiroshi Onishi  3 , Keiichi Jingu  1
Affiliations

Utilization and regional disparities of radiotherapy in cancer treatment in Japan: a longitudinal study using NDB open data

Kazuya Takeda et al. J Radiat Res. .

Abstract

The National Database of Health Insurance Claims and Specific Health Checkups of Japan (NDB) is a database that stores anonymized information on medical receipts and health checkups in Japan. The NDB Open Data is a publicly accessible summary table of the NDB database. To reveal annual trends and regional disparities in radiotherapy utilization in Japan, we analyzed the NDB Open Data tables for a 9-year period from 2014 to 2022. We extracted medical cost codes for radiotherapy management fees and specific types of radiotherapy, such as stereotactic irradiation (STI) and intensity-modulated radiotherapy (IMRT), to analyze nationwide changes over time. To investigate regional disparities, we counted the three subitems representing 3-dimensional conformal radiotherapy (3D-CRT), IMRT, and STI for each prefecture per year. The utilization of advanced radiotherapy techniques, such as IMRT (199% increase), increased, while the use of simpler forms of irradiation, such as 1 or 2-opposite fields irradiation (40% decrease), decreased in the period from 2014 to 2022. Regarding regional disparities, the coefficients of variation in 47 prefectures for 3D-CRT remained relatively stable at 0.17 in 2014 and 0.18 in 2022, while the coefficients of variation for IMRT and STI decreased from 0.64 and 0.39 in 2014 to 0.31 and 0.36 in 2022, respectively. The popularization of IMRT was correlated with the number of certified radiation oncologists in the prefecture. In conclusion, although the utilization of high-precision radiotherapy in Japan has been increasing and regional differences have been diminishing, there are still persistent disparities.

Keywords: IMRT; NDB open data; STI; radiotherapy; regional disparity.

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Conflict of interest statement

The authors declare they have no competing interests on this study.

Figures

Fig. 1
Fig. 1
Temporal changes in number of medical fee claims for various types of radiotherapy.
Fig. 2
Fig. 2
Map plot of the number of claims per 100 000 population in each prefecture relative to the national average each year for three different types of radiotherapy.
Fig. 3
Fig. 3
Temporal changes in coefficient of variation of count of three different types of radiotherapy.
Fig. 4
Fig. 4
Distribution of the number of certified radiation oncologists per 100 000 population and number of claims per treatment in each prefecture in 2014 and 2022. Data for the number of certified radiation oncologists were obtained from the nearest available year, 2012 and 2022 for 2014 and 2022, respectively.
Fig. 5
Fig. 5
Changes over time in the use of three different types of radiotherapy per population across each region.
See this image and copyright information in PMC

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References

    1. Numasaki H, Nakada Y, Okuda Y et al. Japanese structure survey of radiation oncology in 2015. J Radiat Res 2022;63:230–46. 10.1093/jrr/rrab129. - DOI - PMC - PubMed
    1. Katano A, Minamitani M, Yamashita H, Nakagawa K. National Survey of radiotherapy utilization trends from 2015 to 2019, based on the National Database of Health Insurance Claims and Specific Health Checkups of Japan. JMA J 2023;6:342–5. 10.31662/jmaj.2022-0142. - DOI - PMC - PubMed
    1. Aoyama T, Koide Y, Shimizu H et al. Trends and distribution of external radiation therapy facilities in Japan based on survey of medical institutions from the Ministry of Health, Labour and Welfare. J Radiat Res 2024;65:328–36. 10.1093/jrr/rrae014. - DOI - PMC - PubMed
    1. Ministry of Health, Labour and Welfare . National Database of Health Insurance Claims and Specific Health Checkups of Japan. Japan: Ministry of Health, Labour and Welfare. https://www.mhlw.go.jp/stf/seisakunitsuite/bunya/kenkou_iryou/iryouhoken... (16 July 2024, date last accessed).
    1. Ministry of Health . Labour and Welfare. NDB Open Data. Japan: Ministry of Health, Labour and Welfare. https://www.mhlw.go.jp/stf/seisakunitsuite/bunya/0000177182.html (16 July 2024, date last accessed).