Inequality in cancer survival rates among industrial sectors in Japan: an analysis of two large merged datasets

Abstract

Objectives: Little is known about the specific prognosis of cancer among workers in different industrial sectors. The aim of this study is to demonstrate cancer survival inequality by industry sectors. Methods: Using multicenter inpatient data (1984−2017) and a regional cancer registry in Japan (1995–2018), we merged these two anonymized datasets. Based on standardized national classifications, cases were grouped according to the longest-held employment in primary, secondary, or tertiary industrial sectors. Data regarding smoking, alcohol consumption, and tumor staging at diagnosis were also extracted. We estimated the 5-year survival rates for common cancers using the Kaplan-Meier method to identify inequalities among industrial sectors. Cox proportional hazard model was used to calculate the hazard ratio (HR) of industry sectors. Results: A total of 13,234 cases were merged from two datasets. Among these, 8,794 cases were defined as common cancers (prostate, kidney, bladder, esophagus, stomach, liver, pancreas, colon, breast, and lung). Five-year survival was significantly (p=0.025) shorter for primary industrial sector (43.1%) compared with secondary sector (54.5%) and tertiary sector (56.9%). The adjusted HR for secondary and tertiary sectors versus primary sector was 0.963 (95% confidence interval [CI], 0.649–1.429). Bladder cancer in secondary and tertiary sectors showed a significantly higher survival rate than in the primary sector (p<0.0001), but the HR of secondary and tertiary sectors was 0.049 (95% CI, 0.021–0.153). Conclusions: This study revealed the potential of industrial sector inequalities with regard to the prognosis of cancers in Japan.