007 - Monitoring of area-based socioeconomic inequalities in cancer survival using nationwide population-based cancer registry data in Japan

Introduction
In Japan, during the 1960s, a limited number of prefectures started regional cancer registries. However, in 2016, the operation of nationwide cancer registration began, based on the Act on Promotion of Cancer Registries. Since this time, the government has collected data on all cancer patients from all hospitals in Japan. For the first time, we can report cancer survival based on nationwide cancer registry data. Health inequalities have become of increasing concern in Japan and the government has been targeting a "reduction in the gap in healthy life expectancy" in the national health plan "Health Japan 21" since 2013. The National Cancer Plan includes "equalization of cancer treatment" as a goal but a concrete target was not set as there had been no monitoring of inequalities in cancer survival based on the population-based cancer registry data.

Methods
We analyzed 893,560 cases, first primary malignant cancer patients diagnosed in 2016 and followed-up for at least one year. We calculated one-year net survival by sex, cancer site, stage at diagnosis and quintile of areal deprivation index using the Pohar-Perme method. Background mortality was estimated from the national lifetables of Japan. We used municipality-level areal deprivation indexes to categorize the quintile of the area-based socioeconomic group.

Results
Absolute difference between one-year net survival of patients in the least deprived area and those in the most deprived area ranged from 0.2% (smallest gap, gallbladder) to 12.6% (widest gap, leukemia) in men and -1.3% (kidney) to 8.0% (brain) across cancer sites. By cancer site for all stages, the widest gap was observed for leukemia in men and brain and central nervous system cancer in women. For localized patients, the widest gap in one-year net survival was observed in pancreatic cancer in men and women. For distant metastasis patients, the widest gap was observed in thyroid cancer in men and oral cancer in women.

Discussion
We reported the socioeconomic inequalities in one-year net survival using nationwide population-based cancer registry data, for the first time, in Japan. Even in short-term survival, we observed a wide gap in one-year net survival between patients in the least deprived and the most deprived areas, depending on the cancer site and stage at diagnosis. Further analysis will be needed, using a multivariate excess hazard model, to control the differences in age distribution among the quintiles of the areal deprivation groups. Differences in stage at diagnosis among the socioeconomic groups might also influence the gaps in cancer survival. In order to use these findings as target figures to monitor inequalities in cancer outcome, as an assurance of equity among cancer treatment, other important factors, such as access to specialized hospitals, patient comorbidities, and performance status, also need to be considered. We also need to understand the mechanisms of socioeconomic inequalities in cancer outcome, in order to deal with the issue.

health inequalities

cancer survival

cancer control 

Beginner

Knowledge

International Conference on Health Policy Statistics 2023