Clinical epidemiological study on a rational screening program for colorectal cancer

本研究旨在评价两日免疫化学粪便潜血试验（IFOBT）筛查结直肠癌（CRC）的效果。结果表明，筛查后CRC死亡风险降低。在过去5年内筛查的患者的风险降低约50 - 70%，即病例诊断前1 - 5年筛查的患者的比值比范围为0.33（95%置信区间：0.13-0.84）至0.52（0.27-1.01）。通过比较同一时间段内研究区域内发生的CRC病例与其对照之间的筛选史，将自我选择偏倚估计为CRC的发生率比：筛选应答者与无应答者的发生率。筛选后晚期的发生率比（自我选择偏倚的近似值）不小于1.0，表明自我选择偏倚不是本研究主要分析中获得的低比值比的显著贡献因素。这些结果表明，使用IFOBT进行CRC筛查可以降低癌症的死亡率。

The present study was intended to evaluate efficacy of screening program for colorectal cancer(CRC) using the two-day immunochemical fecal occult blood test(IFOBT). It was shown that risk of dying of CRC reduced after screening. Approximately 50 to 70% of risk reduction was suggested for those screened within the past 5 years, ie odds ratios for those screened 1 to 5 years before case diagnosis ranged 0.33(95% confidence interval: 0.13-0.84) to 0.52(0.27-1.01). By comparing screening histories between incident CRC cases in the study areas during the same time period and their controls, self-selection bias was estimated as incidence ratio of CRC: incidence in screening responders to that in non-responders. Incidence ratio in the late phase after screening, which would be an approximate value of self-selection bias, was not less than 1.0 showing that self-selection bias was not a significant contributor to the low odds ratios obtained in the main analysis of the present study. These results indicate that CRC screening program with IFOBT can reduce mortality from the cancer.