Objectives: We reviewed the operational definitions of colorectal cancer (CRC) from studies using the Korean National Health Insurance Service (NHIS) and compared CRC incidence derived from the commonly used operational definitions in the literature with the statistics reported by the Korea Central Cancer Registry (KCCR). Methods: We searched the MEDLINE and KoreaMed databases to identify studies containing operational definitions of CRC, published until January 15, 2021. All pertinent data concerning the study period, the utilized database, and the outcome variable were extracted. Within the NHIS-National Sample Cohort, age-standardized incidence rates (ASRs) of CRC were calculated for each operational definition found in the literature between 2005 and 2019. These rates were then compared with ASRs from the KCCR. Results: From the 62 eligible studies, 9 operational definitions for CRC were identified. The most commonly used operational definition was “C18-C20” (n=20), followed by “C18-C20 with claim code for treatment” (n=3) and “C18-C20 with V193 (code for registered cancer patients’ payment deduction)” (n=3). The ASRs reported using these operational definitions were lower than the ASRs from KCCR, except for “C18-C20 used as the main diagnosis.” The smallest difference in ASRs was observed for “C18-C20,” followed by “C18- C20 with V193,” and “C18-C20 with claim code for hospitalization or code for treatment.” Conclusions In defining CRC patients utilizing the NHIS database, the ASR derived through the operational definition of “C18-C20 as the main diagnosis” was comparable to the ASR from the KCCR. Depending on the study hypothesis, operational definitions using treatment codes may be utilized.

OBJECTIVES: Biliary tract cancers (BTCs) are rare but highly fatal. Although the etiology of BTC is poorly understood, gallstones are proposed to be a major risk factor. We conducted a systematic review and meta-analysis to examine the associations between gallstone characteristics and BTC risk. METHODS: We searched the MEDLINE, Embase, and Cochrane Central databases and systematically reviewed cohort and case-control studies published before April 9, 2018. All the included studies reported appropriate risk estimates and confidence intervals (CIs) for associations between the presence, size, number, or duration of gallstones and the risk of BTC, including gallbladder cancer (GBC), extrahepatic bile duct cancer (EBDC), and ampulla of Vater cancer (AOVC). Summary odds ratios (ORs) and their 95% CIs were calculated using a random-effects model in the meta-analysis. Subgroup analyses were conducted to inspect sources of potential heterogeneity, and the Egger test was performed to assess publication bias. RESULTS: Seven cohort studies and 23 case-control studies in Asian, European, and American populations were included. The presence of gallstones was associated with an increased risk of BTC (OR, 4.38; 95% CI, 3.23 to 5.93; I2=91.2%), GBC (OR, 7.26; 95% CI, 4.33 to 12.18), EBDC (OR, 3.17; 95% CI, 2.24 to 4.50), and AOVC (OR, 3.28; 95% CI, 1.33 to 8.11). Gallstone size (>1 vs. <1 cm; OR, 1.88; 95% CI, 1.10 to 3.22) was significantly associated with the risk of GBC. CONCLUSIONS Gallstone characteristics, such as presence, size, and number, are associated with an increased risk of BTC. However, significantly high heterogeneity in the meta-analyses is a limitation of this study.

OBJECTIVES: Biliary tract cancers (BTCs) are rare but highly fatal. Although the etiology of BTC is poorly understood, gallstones are proposed to be a major risk factor. We conducted a systematic review and meta-analysis to examine the associations between gallstone characteristics and BTC risk. METHODS: We searched the MEDLINE, Embase, and Cochrane Central databases and systematically reviewed cohort and case-control studies published before April 9, 2018. All the included studies reported appropriate risk estimates and confidence intervals (CIs) for associations between the presence, size, number, or duration of gallstones and the risk of BTC, including gallbladder cancer (GBC), extrahepatic bile duct cancer (EBDC), and ampulla of Vater cancer (AOVC). Summary odds ratios (ORs) and their 95% CIs were calculated using a random-effects model in the meta-analysis. Subgroup analyses were conducted to inspect sources of potential heterogeneity, and the Egger test was performed to assess publication bias. RESULTS: Seven cohort studies and 23 case-control studies in Asian, European, and American populations were included. The presence of gallstones was associated with an increased risk of BTC (OR, 4.38; 95% CI, 3.23 to 5.93; I2=91.2%), GBC (OR, 7.26; 95% CI, 4.33 to 12.18), EBDC (OR, 3.17; 95% CI, 2.24 to 4.50), and AOVC (OR, 3.28; 95% CI, 1.33 to 8.11). Gallstone size (>1 vs. <1 cm; OR, 1.88; 95% CI, 1.10 to 3.22) was significantly associated with the risk of GBC. CONCLUSIONS Gallstone characteristics, such as presence, size, and number, are associated with an increased risk of BTC. However, significantly high heterogeneity in the meta-analyses is a limitation of this study.