Watanabe Sintaroo, Fukai Kota, Tatemichi Masayuki
Safety & Health Group, Japan Marine United Corporation Kure Shipyard, Kure, 737-0027 Japan.
Department of Preventive Medicine, Tokai University School of Medicine, Isehara, 259-1193 Japan.
J Occup Health. 2024 Jan 4;66(1). doi: 10.1093/joccuh/uiae072.
This study aimed to estimate the probability of observing 2 cases of the same cancer type in a workplace with 300 employees, to help investigation of occupational cancer.
We assumed a workplace where chemicals are handled, employing 300 males aged 15 to 64, with an age distribution standardized to Japan's population from 2016 to 2019. Using national cancer statistics for newly diagnosed cases among males in this age range and period, we calculated the expected number of cancer cases for the workplace over a 1- and 10-year period. We computed standardized incidence ratios (SIRs) for 2 instances of the same cancer type within these time frames and estimated the time required for the SIR to reach 2.0 and its lower 95% CI limit (LL) to reach 1.0.
The SIR for any cancer type exceeded 10 and was significantly high when 2 cases occurred within 1 year. Over 10 years, the SIR remained significantly high in some cancer types. The observation periods required for SIR to reach 2.0 and LL to reach 1.0 for any cancer type were at least 5.4 and at least 1.7 years, respectively.
Considering that over 99% of Japanese workplaces employ fewer than 300 people, the likelihood of observing the same cancer type within 1 year is low. This study enhances our understanding of occupational cancer incidence and supports the integration of such data into prevention strategies.
本研究旨在估计在一个有300名员工的工作场所中观察到2例相同癌症类型病例的概率，以协助职业性癌症的调查。
我们假设一个处理化学品的工作场所，雇佣300名年龄在15至64岁之间的男性，其年龄分布根据2016年至2019年日本人口进行了标准化。利用该年龄范围和时期内男性新诊断病例的国家癌症统计数据，我们计算了该工作场所在1年和10年期间的癌症病例预期数量。我们计算了在这些时间框架内同一癌症类型出现2例的标准化发病比（SIR），并估计了SIR达到2.0及其较低的95%置信区间下限（LL）达到1.0所需的时间。
当1年内出现2例病例时，任何癌症类型的SIR均超过10且显著偏高。在10年期间，某些癌症类型的SIR仍显著偏高。任何癌症类型的SIR达到（至少）2.0和LL达到（至少）1.0所需的观察期分别至少为5.4年和至少1.7年。
考虑到超过99%的日本工作场所员工人数少于300人，在1年内观察到相同癌症类型的可能性较低。本研究增进了我们对职业性癌症发病率的理解，并支持将此类数据纳入预防策略。
