Chang Kyun Choi

Purpose: To develop the 2025 update to the Korean colorectal cancer (CRC) screening guidelines by systematically evaluating recent evidence, integrating domestic data, and addressing changes since the 2015 guideline revision, thereby providing an evidence-based standard for clinicians and policymakers.Methods: A multidisciplinary committee developed the guidelines using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) methodology. The process included formulation of three key questions addressing screening efficacy, diagnostic accuracy, and optimal screening age and interval. A systematic review of international guidelines and primary literature was conducted, yielding 327 eligible studies. In addition, a utility-based analysis using a Markov model was performed to determine optimal screening ages and intervals.Results: The evidence synthesis identified high-certainty evidence supporting the use of the fecal immunochemical test (FIT) for reducing CRC mortality and moderate-certainty evidence for colonoscopy. Evidence for computed tomographic colonography (CTC) and stool DNA testing was rated as very low certainty. Based on the evidence review and cost-utility analysis, the committee conditionally recommends CRC screening for asymptomatic, average-risk adults aged 45–74 years using either colonoscopy every 10 years or FIT every 1–2 years. CTC and stool DNA testing were not recommended owing to insufficient evidence.Conclusion: The 2025 Korean Guidelines for Colorectal Cancer Screening present updated, evidence-based recommendations tailored to the domestic healthcare context. By conditionally endorsing both colonoscopy and FIT for individuals aged 45–74 years, these guidelines aim to improve population-level screening effectiveness and reduce the burden of CRC in South Korea.

Background: C-reactive protein (CRP) is a widely used inflammatory biomarker that has been related to colorectal cancer risk. However, observational studies are prone to confounding and reverse causality. Methods: We conducted a two-sample Mendelian randomization using CRP genome-wide association study (GWAS) data from 59,605 Korean individuals and colorectal cancer GWAS data from 23,572 cases and 48,700 controls from an East Asia population. The analysis had 80% power to detect an OR of 1.12 for colorectal cancer risk per twofold increase in CRP levels. Results: Genetically predicted serum CRP levels (per twofold increase) were not significantly associated with colorectal cancer risk (inverse-variance weighted OR, 0.995; 95% confidence interval, 0.893–1.109; P value, 0.929). Null findings remained consistent in sensitivity analyses excluding the horizontally pleiotropic effect. Conclusions: Despite sufficient statistical power, little evidence supported a causal association between CRP and colorectal cancer risk in East Asians. Impact: Our findings suggest that CRP is unlikely to be a key determinant of colorectal carcinogenesis, aligning with prior studies in European populations.

Introduction: Since the early 2000s, South Korea has implemented tobacco control policies; however, smoking behaviors have not been sufficiently evaluated through age-period-cohort analysis. Methods: A hierarchical age-period-cohort model was applied to two nationwide surveys, including socioeconomic and lifestyle factors. Age was defined at participation, period as survey year, and cohort as birth year. Current smoking prevalence was analyzed among 54 917 men and 69 551 women aged 12–80 years from the Korea National Health and Nutrition Examination Survey I–VIII (1998, 2001, 2005, and 2007–2023). Cigarettes per day (CPD) were assessed among 518 786 male and 44 410 female smokers aged 19–80 from the Korea Community Health Survey 2008–2022. Results: Smoking prevalence declined after the age of the early 20s and early 40s among men and women, respectively. Among men, the cohort effect on smoking prevalence stagnated starting with the 1980s birth cohort, whereas in women, a decline was observed from the 1990s birth cohort onward. Disparities in smoking widened, particularly among individuals with lower education levels or current drinkers (p for interaction <.001). CPD exhibited an inverted U-shape, peaking in the late 40s, with minimal variation (<1 CPD) among women. After the coronavirus disease-2019 pandemic, CPD increased only among women (p < .001), while cohort effects on CPD were not significant. Conclusions: The decline in smoking prevalence stagnated, with widening disparities by educational attainment, marital status, and alcohol consumption. Policies should address these disparities and include sex-specific strategies to accelerate smoking reduction. Implications: This study highlights the stagnation in the decline of smoking prevalence in South Korea, particularly among recent birth cohorts with lower educational attainment and current alcohol consumption. Notably, an increase in cigarette consumption following the coronavirus disease-2019 pandemic was observed only among women. These findings underscore the importance of implementing gender-responsive and equity-oriented tobacco control policies that address behavioral and socioeconomic disparities to sustain progress in smoking reduction.

Objectives: Accurate and complete cancer staging is essential for effective prognosis and treatment planning. This study investigated the feasibility of enhancing the completeness of tumor‐node‐metastasis (TNM) staging by integrating Surveillance, Epidemiology, and End Results (SEER) Summary Stage data.Methods: We analyzed data from 5 cancer types (stomach, colorectum, liver, lung, and breast) in Korea (2012-2017). The study assessed the impact of supplementing missing TNM information with SEER Summary Stage data on both staging completeness and 5‐year relative survival rates.Results: The study included 173 061 stomach cancer, 159 199 colorectal cancer, 89 639 liver cancer, 137 103 lung cancer, and 110 286 breast cancer patients. The percentage of missing TNM stage data varied by cancer type, ranging from 65.1% (breast cancer) to 93.0% (liver cancer). Supplementation significantly reduced missing values—most notably in stomach cancer, where missing data dropped by 50.6 percentage points (%p), followed by liver (21.5%p) and breast cancers (13.6%p). For stomach cancer, supplementation led to a 3.6%p decrease in stage I survival rates, whereas liver cancer exhibited the most pronounced changes, with stage IV survival rates declining from 17.7% to 7.9%.Conclusions: Integrating SEER Summary Stage data enhances TNM staging completeness. However, further evaluation incorporating treatment information is essential.

Choi CK, et al. J Korean Med Sci. 2024 May;39(20):e169. https://doi.org/10.3346/jkms.2024.39.e169

OBJECTIVES: This study investigated regional disparities in the incidence of 8 major cancers at the municipal level in Korea during 1999-2018 and evaluated the presence or absence of hot spots of cancer clusters during 2014-2018.METHODS: The Korea National Cancer Incidence Database was used. Age-standardized incidence rates were calculated by gender and region at the municipal level for 4 periods of 5 years and 8 cancer types. Regional disparities were calculated as both absolute and relative measures. The possibility of clusters was examined using global Moran’s I with a spatial weight matrix based on adjacency or distance.RESULTS: Regional disparities varied depending on cancer type and gender during the 20-year study period. For men, the regional disparities of stomach, colon and rectum, lung, and liver cancer declined, and those of thyroid and prostate cancer recently decreased, despite an overall increasing incidence. For women, regional disparities in stomach, colon and rectum, lung, liver, and cervical cancer declined, that of thyroid cancer recently decreased, despite an overall increasing incidence, and that of breast cancer steadily increased. In 2014-2018, breast cancer (I, 0.61; 95% confidence interval [CI], 0.53 to 0.70) showed a high probability of cancer clusters in women, and liver cancer (I, 0.48; 95% CI, 0.40 to 0.56) showed a high probability of cancer clusters in men.CONCLUSIONS: Disparities in cancer incidence that were not seen at the national level were discovered at the municipal level. These results could provide important directions for planning and implementing local cancer policies.

OBJECTIVES: Elevated C-reactive protein (CRP) levels are associated with an increased risk for colorectal cancer (CRC), as well as a poor prognosis, but it remains unclear whether these associations are causal. This study examined the potential causality between CRP levels and CRC survival using 2-sample Mendelian randomization (MR).METHODS: From the Korean Genome and Epidemiology Study, a genome-wide association study (n=59,605), 7 single-nucleotide polymorphisms (SNPs) related to log2-transformed CRP levels were extracted as instrumental variables for CRP levels. The associations between the genetically predicted CRP and CRC-specific and overall mortality among CRC patients (n=6,460) were evaluated by Aalen’s additive hazard model. The sensitivity analysis excluded a SNP related to the blood lipid profile.RESULTS: During a median of 8.5 years of follow-up, among 6,460 CRC patients, 2,676 (41.4%) CRC patients died from all causes and 1,622 (25.1%) died from CRC. Genetically predicted CRP levels were not significantly associated with overall or CRC-specific mortality in CRC patients. The hazard difference per 1,000 person-years for overall and CRC-specific mortality per 2-fold increase in CRP levels was -2.92 (95% confidence interval [CI], -14.05 to 8.21) and -0.76 (95% CI, -9.61 to 8.08), respectively. These associations were consistent in a subgroup analysis according to metastasis and a sensitivity analysis excluding possible pleiotropic SNPs.CONCLUSIONS: Our findings do not support a causal role for genetically predisposed CRP levels in CRC survival.

Choi CK, et al. Korean Circ J. 2023 Jul;53:e57. https://doi.org/10.4070/kcj.2023.0089

Improved diabetes management in primary care is essential for reducing the public health burden of diabetes, and various programs are being implemented in Korea for this purpose. Although the Health Insurance Review and Assessment (HIRA) evaluates the quality of type 2 diabetes management in primary care clinics and hospitals, it is unclear whether the implementation of these evaluations is related to the adequate management of complications in diabetic patients. We evaluated the association between the proportion of clinics managing diabetes well and lifestyles and uptake of screening for complications in 24,620 diabetic participants of the 2019 Korean Community Health Survey (KCHS). Multivariate multilevel logistic regression was performed to evaluate the fixed effect of the district-level variable and the heterogeneity among districts. The proportion of clinics with good diabetes management per 10,000 inhabitants was positively related to screening for diabetes complications. Furthermore, this district variable was significantly related to engaging in walking activity (Odds ratio: 1.39, 95% CI: 1.10–1.76) and sufficiently explained the heterogeneity among districts. However, current smoking and weight control were not associated with the proportion of clinics with good diabetes management. The financial incentives to primary care clinics would improve the primary prevention of diabetic complications.

Objective: To investigate the association between obesity and self‐rated oral health (SROH). This study examined the cross‐sectional associations between body mass index (BMI) and SROH in Korean adults.Materials and methods: This study used data from 217 304 adults (100 110 men and 117 194 women aged > 19 years) from the 2017 Korean Community Health Survey. Participants were categorised into six ordinal groups based on BMI: underweight (2), normal weight (18.5‐22.9 kg/m²), overweight (23.0‐24.9 kg/m²), obese‐I (25.0‐27.4 kg/m²), obese‐II (27.5‐29.9 kg/m²) or obese‐III (≥30.0 kg/m²). SROH was assessed using responses to the question, “How do you rate your oral health, including your teeth and gums?” rated on a 5‐point scale. SROH was categorised as “good” (reported as “fair,” “good” or “very good”) or “poor” or “very poor.” Age‐ and sex‐stratified associations between BMI categories and poor SROH were assessed using ordinal logistic regression analysis with sampling weights.Results: The age‐adjusted odds ratio (OR) for poor SROH according to BMI levels was lowest in the overweight group in both men and women. In men, the OR for poor SROH was 2.03 (99% confidence interval [CI], 1.72‐2.39) in the underweight group, 1.17 (99% CI, 1.17‐1.25) in the normal group, 1.05 (99% CI, 0.98‐1.13) in the obese‐I group, 1.08 (99% CI, 0.98‐1.18) in the obese‐II group and 1.36 (99% CI, 1.20‐1.55) in the obese‐III group. In women, the OR was 1.18 (99% CI, 1.07‐1.31) in the underweight group, 1.01 (99% CI, 0.95‐1.07) in the normal group, 1.07(99% CI, 0.99‐1.16) in the obese‐I group, 1.16 (99% CI, 1.04‐1.30) in the obese‐II group and 1.39 (99% CI, 1.20‐1.62) in the obese‐III group. From the restricted cubic spline models in both sexes, BMI showed a J‐shaped association with poor and very poor SROH in men and women. In a stratified analysis by age group and sex, men and older women in the underweight group had poorer SROH than those in overweight group.Conclusion: In a nationally representative sample of Korean adults, there was a J‐shaped association between BMI and poor SROH, with the highest risk in the underweight group amongst men and in the obese‐III group amongst women. Furthermore, in men and women over 65 years of age, underweight and obesity were associated with poorer SROH.