Cancer- and noncancer-specific cumulative incidence of death after exposure to polychlorinated biphenyls and dioxins: A competing risk analysis among Yusho patients

Background In competing risks settings, the cause-specific cumulative incidence function is of great interest since it quantifies cumulative risk in the presence of other causes. To date, however, long-term cancer- and noncancer-specific mortality in Yusho patients exposed to polychlorinated biphenyls (PCBs) and dioxin-related compounds has not been estimated. Methods We identified vital status and cause of death for Yusho patients between 1968 and 2017. Risk of cancer- and noncancer-specific mortality was estimated using a flexible hazards-based regression model, with accounting for competing events. Results In total, 1664 Yusho patients with 63,566 person-years of follow-up were included in the analysis. 50-year cumulative incidence of cancer mortality was 12.4% (95% confidence interval [CI], 10.5-14.7) in males and 4.7% (95% CI, 3.5-6.4) in females (difference, 7.7 percentage points [95% CI, 5.2-10.2]; adjusted hazard ratio for males, 2.61 [95% CI, 1.93-3.52]). For noncancer, the 50-year cumulative incidence of mortality was 35.4% (95% CI, 32.8-38.3) in males and 35.6% (95% CI, 33.3-38.1) in females (difference, -0.2 percentage points [95% CI, -3.5 to 3.1]; adjusted hazard ratio for males, 1.51 [95% CI, 1.26-1.82]). Conclusions These findings confirm that male Yusho patients have a significantly higher risk of cumulative incidence of cancer-specific mortality than female Yusho patients. Our findings might be useful in providing Yusho patients with more accurate information on cancer prognosis and survivorship and help determine more appropriate disease management.