Cost-Utility Analysis for Colorectal Cancer Screening According to the Initiating Age of National Cancer Screening Program in Korea.

BACKGROUND: This study aimed to identify the most cost-effective strategy for colorectal cancer screening using the fecal immunochemical test (FIT), focusing on screening initiation age in Korea. METHODS: We designed Markov simulation models targeting individuals aged 40 years or older. Twelve strategies combining screening initiation ages (40, 45, or 50 years old), termination ages (80 or no limit), and intervals (1 or 2 years) were modeled, and the most cost-effective strategy was selected. The robustness of the results was confirmed using one-way and probabilistic sensitivity analyses. Furthermore, the cost-effectiveness of the qualitative and quantitative FIT methods was verified using scenario analysis. RESULTS: The 2-year interval strategy with a screening age range of 45-80 years was the most cost-effective (incremental cost-utility ratio = KRW 7,281,646/quality adjusted life years). The most sensitive variables in the results were transition rate from advanced adenoma to local cancer and discount rate. The uncertainty in the model was substantially low. Moreover, strategies starting at the age of 40 years were also cost-effective but considered suboptimal. The scenario analysis showed that there was no significant difference in cost-effectiveness between strategies with various relative screening ratio of quantitative and qualitative method. CONCLUSION: The screening method for advancing the initiation age, as presented in the 2015 revised national screening recommendations, was superior regarding cost-effectiveness. This study provides a new paradigm for the development of a national cancer screening system in Korea, which can be utilized as a scientific basis for economic evaluations.

Socioeconomic differences in the perception of inequalities in healthcare utilization and health in South Korea.

This study investigated the lay perception of inequalities in society, healthcare utilization, and health in Korea. We also examined the association between socioeconomic status (SES) and perception of inequalities. Data from an online survey on the perception of health and healthcare inequalities related to cancer conducted between October 19, 2021, and November 12, 2021, were used. Data of 3,769 participants aged 20 to 74 years from 17 provinces were analyzed. We examined the perceived level of inequalities according to SES or residential area using frequency analysis, a t-test or analysis of variance (ANOVA), multiple linear regression analysis, and multiple logistic regression analysis. The mean score for perception of social inequality was 5.99 [Standard Deviation (SD) = 1.95] and that for perception of healthcare utilization inequality was 4.75 (SD = 1.96). The perception rate of health inequality according to SES and residential area was approximately 59 % and 61 %, respectively. Higher the income level, lower the level of perception of social inequalities ß = -0.22, p < 0.01). Higher the education level, higher the level of perception of healthcare utilization inequalities (ß = 0.21, p < 0.01). Higher the education level, higher the level of perception of health inequalities according to SES or residential area [adjusted odds ratio (aOR): 2.33 (95 % CI: 1.48, 3.66); aOR: 2.73 (95 % CI: 1.73, 4.31)]. Socioeconomic inequalities were observed in the perception of inequalities in healthcare utilization and health. Policymakers should establish policies to bridge the gap between perceived healthcare utilization inequalities and health inequalities. Future research should investigate the perception of healthcare utilization and health inequalities.

Socioeconomic inequality in organized and opportunistic screening for gastric cancer: results from the Korean National Cancer Screening Survey 2009-2022.

Objectives: This study aimed to evaluate the socioeconomic inequality in gastric cancer (GC) screening in Korea. Socioeconomic inequality was assessed using both organized and opportunistic screening according to income and educational level. Methods: GC screening data were obtained from the 2009-2022 Korean National Cancer Screening Survey. The final analysis included 47,163 cancer-free men and women. The weighted cancer screening rate was estimated using joinpoint regression. The inequality indices were measured in terms of both the absolute slope index of inequality (SII) and the relative index of inequality (RII) using the Poisson regression model. Results: The organized screening rate for GC increased from 38.2% in 2009 to 70.8% in 2022, whereas the opportunistic screening rate decreased from 18.8 to 4.5%. Regarding educational inequality, a negative SII value was observed [-3.5, 95% confidence interval (CI), -7.63-0.83%] in organized screening, while a positive SII (9.30%; 95% CI, 6.69-11.91%) and RII (1.98%; 95% CI, 1.59-2.46) were observed in opportunistic screening. Furthermore, income inequality was not found in organized GC screening; however, overall SII and RII for opportunistic screening were 7.72% (95% CI, 5.39-10.5) and 1.61 (95% CI, 1.42-1.81), respectively. Conclusion: Organized screening rates have grown gradually over time and account for the majority of GC screenings in South Korea. While no socioeconomic inequalities were found in organized screening, significant socioeconomic inequalities were found in opportunistic screening.

Socioeconomic inequality in organized and opportunistic screening for colorectal cancer: results from the Korean National Cancer Screening Survey, 2009-2021.

OBJECTIVES: This study aimed to investigate socioeconomic status (SES)-based inequality in colorectal cancer (CRC) screening in Korea. We assessed whether the rates of opportunistic and organized CRC screening differed according to income and education levels. METHODS: We analyzed data from the Korean National Cancer Screening Survey of 27,654 cancer-free individuals, aged 50-74 years, from 2009 to 2021. The weighted cancer screening rates with trends were estimated with the average annual percentage change using joinpoint regression. Inequality was calculated in both relative and absolute terms, based on a Poisson regression model. RESULTS: The organized screening rate increased significantly from 22.1% in 2009 to 53.1% in 2020 and 50.6% in 2021, with an average annual change of 8.6% (95% confidence interval [CI], 4.9 to 12.5). In contrast, no significant trend was observed for opportunistic screening. The SES inequality in opportunistic screening uptake was indicated by a slope index of inequality (SII) of 9.74% (95% CI, 6.36 to 13.12), relative index of inequality (RII) of 2.18 (95% CI, 1.75 to 2.70) in terms of education level; and an SII of 7.03% (95% CI, 4.09 to 9.98), RII of 1.81 (95% CI, 1.41 to 2.31) in terms of measured income. Although there was an increasing trend in income inequality, no significant SES inequalities were observed in the overall estimates for organized screening. CONCLUSIONS: Organized CRC screening is effective in improving the participation rate, regardless of SES. However, significant inequalities were found in opportunistic screening, suggesting room for improvement in the overall equity of CRC screening.

Inhalation cancer risk assessment for environmental exposure to hexavalent chromium: Comparison of margin-of-exposure and linear extrapolation approaches.

Hexavalent chromium [Cr(VI)] exists in the ambient air at low concentrations (average upperbound ~0.1 ng/m3) yet airborne concentrations typically exceed EPA's Regional Screening Level for residential exposure (0.012 ng/m3) and other similar benchmarks, which assume a mutagenic mode of action (MOA) and use low-dose linear risk assessment models. We reviewed Cr(VI) inhalation unit risk estimates developed by researchers and regulatory agencies for environmental and occupational exposures and the underlying epidemiologic data, updated a previously published MOA analysis, and conducted dose-response modeling of rodent carcinogenicity data to evaluate the need for alternative exposure-response data and risk assessment approaches. Current research supports the role of non-mutagenic key events in the MOA, with growing evidence for epigenetic modifiers. Animal data show a weak carcinogenic response, even at cytotoxic exposures, and highlight the uncertainties associated with the current epidemiological data used in risk assessment. Points of departure from occupational and animal studies were used to determine margins of exposure (MOEs). MOEs range from 1.5 E+3 to 3.3 E+6 with a median of 5 E+5, indicating that current environmental exposures to Cr(VI) in ambient air should be considered of low concern. In this comprehensive review, the divergent results from default linear and MOE assessments support the need for more relevant and robust epidemiologic data, additional mechanistic studies, and refined risk assessment strategies.

Socioeconomic Inequalities in Cervical and Breast Cancer Screening among Women in Korea, 2005-2015.

PURPOSE: Consistent evidence indicates that cervical and breast cancer screening rates are low among socioeconomically deprived women. This study aimed to assess trends in cervical and breast cancer screening rates and to analyze socioeconomic inequalities among Korean women from 2005 to 2015. MATERIALS AND METHODS: Data from the Korean National Cancer Screening Survey, an annual nationwide cross-sectional survey, were utilized. A total of 19910 women were finally included for analysis. Inequalities in education and household income status were estimated by slope index of inequality (SII) and relative index of inequality (RII), along with calculation of annual percent changes (APCs), to show trends in cancer screening rates. RESULTS: Cervical and breast cancer screening rates increased from 54.8% in 2005 to 65.6% in 2015 and from 37.6% in 2005 to 61.2% in 2015, respectively. APCs in breast cancer screening rates were significant among women with higher levels of household income and education status. Inequalities by household income in cervical cancer screening uptake were observed with a pooled SII estimate of 10.6% (95% CI: 8.1 to 13.2) and RII of 1.4 (95% CI: 1.3 to 1.6). Income inequalities in breast cancer screening were shown to gradually increase over time with a pooled SII of 5.9% (95% CI: 2.9 to 9.0) and RII of 1.2 (95% CI: 0.9 to 1.3). Educational inequalities appeared to diminish over the study period for both cervical and breast cancer screening. CONCLUSION: Our study identified significant inequalities among socioeconomically deprived women in cervical and breast cancer screening in Korea. Especially, income-related inequalities were greater than education-related inequalities, and these were constant from 2005 to 2015 for both cervical and breast cancer screening.

Socioeconomic Inequalities in Colorectal Cancer Screening in Korea, 2005-2015: After the Introduction of the National Cancer Screening Program.

PURPOSE: This study aimed to investigate inequalities in colorectal cancer (CRC) screening rates in Korea and trends therein using the slope index of inequality (SII) and relative index of inequality (RII) across income and education groups. MATERIALS AND METHODS: Data from the Korean National Cancer Screening Survey, an annually conducted, nationwide cross-sectional survey, were utilized. A total of 17174 men and women aged 50 to 74 years were included for analysis. Prior experience with CRC screening was defined as having either a fecal occult blood test within the past year or a lifetime colonoscopy. CRC screening rates and annual percentage changes (APCs) were evaluated. Then, SII and RII were calculated to assess inequality in CRC screening for each survey year. RESULTS: CRC screening rates increased from 23.4% in 2005 to 50.9% in 2015 (APC, 7.8%; 95% CI, 6.0 to 9.6). Upward trends in CRC screening rates were observed for all age, education, and household income groups. Education inequalities were noted in 2009, 2014, and overall pooled estimates in both indices. Income inequalities were inconsistent among survey years, and overall estimates did not reach statistical significance. CONCLUSION: Education inequalities in CRC screening among men and women aged 50 to 74 years were observed in Korea. No apparent pattern, however, was found for income inequalities. Further studies are needed to thoroughly outline socio-economic inequalities in CRC screening.

Socioeconomic Inequalities in Stomach Cancer Screening in Korea, 2005-2015: After the Introduction of the National Cancer Screening Program.

PURPOSE: This study aimed to investigate socioeconomic inequalities in stomach cancer screening in Korea and trends therein across income and education groups. MATERIALS AND METHODS: Data from the Korean National Cancer Screening Survey, a nationwide cross-sectional survey, were utilized. A total of 28913 men and women aged 40 to 74 years were included for analysis. Prior experience with stomach cancer screening was defined as having undergone either an endoscopy or gastrointestinal series within the past two years. The slope index of inequality (SII) and relative index of inequality (RII) were evaluated to check inequalities. RESULTS: Stomach cancer screening rates increased from 40.0% in 2005 to 74.8% in 2015, with an annual percent change of 5.8% [95% confidence interval (CI) 4.2 to 7.5]. Increases in stomach cancer screening rates were observed for all age, education, and household income groups. Inequalities in stomach cancer screening were noted among individuals of differing levels of education, with a pooled SII estimate of 6.14% (95% CI, 3.94 to 8.34) and RII of 1.26 (95% CI, 1.12 to 1.40). Also, income-related inequalities were observed with an SII of 6.93% (95% CI, 4.89 to 8.97) and RII of 1.30 (95% CI, 1.17 to 1.43). The magnitude of inequality was larger for income than for education. CONCLUSION: Both education and income-related inequalities were found in stomach cancer screening, despite a continuous increase in screening rate over the study period. Income-related inequality was greater than education-related inequality, and this was more apparent in women than in men.

Assessment of the mode of action underlying development of forestomach tumors in rodents following oral exposure to ethyl acrylate and relevance to humans.

Chronic repeated gavage dosing of high concentrations of ethyl acrylate (EA) causes forestomach tumors in rats and mice. For two decades, there has been general consensus that these tumors are unique to rodents because of: i) lack of carcinogenicity in other organs, ii) specificity to the forestomach (an organ unique to rodents which humans do not possess), iii) lack of carcinogenicity by other routes of exposure, and iv) obvious site of contact toxicity at carcinogenic doses. In 1986, EA was classified as possibly carcinogenic to humans by the International Agency for Research on Cancer (IARC). However, by applying a MOA analyses and human relevance framework assessment, the weight-of-evidence supports a cytotoxic MOA with the following key events: i) bolus delivery of EA to forestomach lumen and subsequent absorption, ii) cytotoxicity likely due to saturation of enzymatic detoxification, iii) chronic regenerative hyperplasia, and iv) spontaneous mutation due to increased cell replication and cell population. Clonal expansion of initiated cells thus results in late onset tumorigenesis. The key events in this 'wound and healing' MOA provide high confidence in the MOA as assessed by evolved Bradford-Hill Criteria. The weight-of-evidence supported by the proposed MOA, combined with a unique tissue that does not exist in humans, indicates that EA is highly unlikely to pose a human cancer hazard.

Assessment of the mutagenic potential of hexavalent chromium in the duodenum of big blue® rats.

A cancer bioassay on hexavalent chromium Cr(VI) in drinking water reported increased incidences of duodenal tumors in B6C3F1 mice at exposures of 30-180ppm, and oral cavity tumors in F344 rats at 180ppm. A subsequent transgenic rodent (TGR) in vivo mutation assay in Big Blue® TgF344 rats found that exposure to 180ppm Cr(VI) in drinking water for 28days did not increase cII transgene mutant frequency (MF) in the oral cavity (Thompson et al., 2015). Herein, we extend our analysis to the duodenum of these same TgF344 rats. At study termination, duodenum chromium levels were below either the limit of detection or quantification in control rats, but were 24.6±3.8µg/g in Cr(VI)-treated rats. The MF in control (23.2×10-6) and Cr(VI)-treated rats (22.7×10-6) were nearly identical. In contrast, the MF in the duodenum of rats exposed to 1-ethyl-1-nitrosourea for six days (study days 1, 2, 3, 12, 19, 26) increased 24-fold to 557×10-6. These findings indicate that mutagenicity is unlikely an early initiating event in Cr(VI)-induced intestinal carcinogenesis.

Cancer mortality-to-incidence ratio as an indicator of cancer management outcomes in Organization for Economic Cooperation and Development countries.

OBJECTIVES: Assessing long-term success and efficiency is an essential part of evaluating cancer control programs. The mortality-to-incidence ratio (MIR) can serve as an insightful indicator of cancer management outcomes for individual nations. By calculating MIRs for the top five cancers in Organization for Economic Cooperation and Development (OECD) countries, the current study attempted to characterize the outcomes of national cancer management policies according to the health system ranking of each country. METHODS: The MIRs for the five most burdensome cancers globally (lung, colorectal, prostate, stomach, and breast) were calculated for all 34 OECD countries using 2012 GLOBOCAN incidence and mortality statistics. Health system rankings reported by the World Health Organization in 2000 were updated with relevant information when possible. A linear regression model was created, using MIRs as the dependent variable and health system rankings as the independent variable. RESULTS: The linear relationships between MIRs and health system rankings for the five cancers were significant, with coefficients of determination ranging from 49 to 75% when outliers were excluded. A clear outlier, Korea reported lower-than-predicted MIRs for stomach and colorectal cancer, reflecting its strong national cancer control policies, especially cancer screening. CONCLUSIONS: The MIR was found to be a practical measure for evaluating the long-term success of cancer surveillance and the efficacy of cancer control programs, especially cancer screening. Extending the use of MIRs to evaluate other cancers may also prove useful.

Transcriptomic responses in the oral cavity of F344 rats and B6C3F1 mice following exposure to Cr(VI): Implications for risk assessment.

Exposure to hexavalent chromium [Cr(VI)] in drinking water was previously reported to increase oral tumor incidence in F344 rats. To investigate the mode of action for these tumors, transcriptomic profiles in oral mucosa samples of F344 rats and B6C3F1 mice were analyzed following exposure to 0.1-180 ppm Cr(VI) for 7 or 90 days. In rats, genome-wide microarray analyses identified no significantly differentially expressed genes (DEGs) at either time point. In mice, 14 and 1 DEGs were respectively identified after 7 and 90 days of exposure. Therefore, relaxed statistical criteria were employed to identify potential DEGs (pDEGs), followed by high-throughput benchmark dose modeling to identify responsive pDEGs for pathway enrichment analysis. This identified 288 and 168 pDEGs in the rat oral mucosa, of which only 20 and 7 showed evidence of dose-response. No significant pathway enrichment was obtained with either pDEG or dose-responsive pDEG lists. Similar results were obtained in mice. These analyses indicate a negligible transcriptional response in the oral mucosa of both species. Comparison of the total number of gene changes in the oral mucosa of rats and mice with responses in the duodenum of animals from the same study demonstrated remarkable dose-response concordance across tissues and species as a function of tissue chromium concentration. The low chromium levels in the oral mucosa and negligible transcript response are consistent with an absence of tissue lesions. These findings are used to compare the merits of linear and nonlinear approaches for deriving toxicity criteria based on the oral tumors in rats. Environ. Mol. Mutagen. 57:706-716, 2016. © 2016 The Authors. Environmental and Molecular Mutagenesis Published by Wiley Periodicals, Inc.

Inhalation cancer risk assessment of cobalt metal.

Cobalt compounds (metal, salts, hard metals, oxides, and alloys) are used widely in various industrial, medical and military applications. Chronic inhalation exposure to cobalt metal and cobalt sulfate has caused lung cancer in rats and mice, as well as systemic tumors in rats. Cobalt compounds are listed as probable or possible human carcinogens by some agencies, and there is a need for quantitative cancer toxicity criteria. The U.S. Environmental Protection Agency has derived a provisional inhalation unit risk (IUR) of 0.009 per µg/m(3) based on a chronic inhalation study of soluble cobalt sulfate heptahydrate; however, a recent 2-year cancer bioassay affords the opportunity to derive IURs specifically for cobalt metal. The mechanistic data support that the carcinogenic mode of action (MOA) is likely to involve oxidative stress, and thus, non-linear/threshold mechanisms. However, the lack of a detailed MOA and use of high, toxic exposure concentrations in the bioassay (≥1.25 mg/m(3)) preclude derivation of a reference concentration (RfC) protective of cancer. Several analyses resulted in an IUR of 0.003 per µg/m(3) for cobalt metal, which is ∼3-fold less potent than the provisional IUR. Future research should focus on establishing the exposure-response for key precursor events to improve cobalt metal risk assessment.

Inhalation cancer risk assessment of hexavalent chromium based on updated mortality for Painesville chromate production workers.

The exposure-response for hexavalent chromium (Cr(VI))-induced lung cancer among workers of the Painesville Ohio chromate production facility has been used internationally for quantitative risk assessment of environmental and occupational exposures to airborne Cr(VI). We updated the mortality of 714 Painesville workers (including 198 short-term workers) through December 2011, reconstructed exposures, and conducted exposure-response modeling using Poisson and Cox regressions to provide quantitative lung cancer risk estimates. The average length of follow-up was 34.4 years with 24,535 person-years at risk. Lung cancer was significantly increased for the cohort (standardized mortality ratio (SMR)=186; 95% confidence interval (CI) 145-228), for those hired before 1959, those with >30-year tenure, and those with cumulative exposure >1.41 mg/m(3)-years or highest monthly exposures >0.26 mg/m(3). Of the models assessed, the linear Cox model with unlagged cumulative exposure provided the best fit and was preferred. Smoking and age at hire were also significant predictors of lung cancer mortality. Adjusting for these variables, the occupational unit risk was 0.00166 (95% CI 0.000713-0.00349), and the environmental unit risk was 0.00832 (95% CI 0.00359-0.0174), which are 20% and 15% lower, respectively, than values developed in a previous study of this cohort.

Assessment of the mutagenic potential of Cr(VI) in the oral mucosa of Big Blue® transgenic F344 rats.

Exposure to high concentrations of hexavalent chromium [Cr(VI)] in drinking water was associated with an increased incidence of oral tumors in F344 rats in a 2-year cancer bioassay conducted by the National Toxicology Program. These tumors primarily occurred at 180 ppm Cr(VI) and appeared to originate from the gingival mucosa surrounding the upper molar teeth. To investigate whether these tumors could have resulted from a mutagenic mode of action (MOA), a transgenic mutation assay based on OECD Test Guideline 488 was conducted in Big Blue(®) TgF344 rats. The mutagenic oral carcinogen 4-nitroquinoline-1-oxide (4-NQO) served as a positive control. Mutant frequency was measured in the inner gingiva with adjacent palate, and outer gingiva with adjacent buccal tissue. Exposure to 10 ppm 4-NQO in drinking water for 28 days increased mutant frequency in the cII transgene significantly, from 39.1 ± 7.5 × 10(-6) to 688 ± 250 × 10(-6) in the gingival/buccal region, and from 49.8 ± 17.8 × 10(-6) to 1818 ± 362 × 10(-6) in the gingival/palate region. Exposure to 180 ppm Cr(VI) in drinking water for 28 days did not significantly increase the mutant frequency in the gingival/buccal (44.4 ± 25.4 × 10(-6)) or the gingival/palate (57.8 ± 9.1 × 10(-6)) regions relative to controls. These data indicate that high (∼180,000 times expected human exposure), tumorigenic concentrations of Cr(VI) did not significantly increase mutations in the gingival epithelium, and suggest that Cr(VI) does not act by a mutagenic MOA in the rat oral cavity.

Different socioeconomic inequalities exist in terms of the prevention, diagnosis and control of diabetes.

OBJECTIVE: To evaluate socioeconomic disadvantage in prevalence, awareness and control of diabetes in universal coverage healthcare system. METHODS: Data from the fifth KNHNES (2010-12) were analyzed. The sample included 10,208 individuals with diabetes aged ≥30 years. Diabetes was defined by (i) a self-reported previous diagnosis of diabetes made by a physician, (ii) the current use of oral hypoglycaemic agents and/or insulin or (iii) fasting plasma glucose ≥126 mg/dl. Subjects who were first diagnosed by the survey were classified as 'undiagnosed'. Inadequate control was defined as HbA1c ≥6.5%. RESULTS: It was estimated that 26.4% of subjects with diabetes were not aware of their condition and 73.1% of cases of diabetes were not adequately controlled. Inequalities in socioeconomic status were related to the diabetes prevalence in both men and women. Educational level was not predictive of diagnosis or control in men or women, whereas lower household income level was associated with diagnosis in men only. CONCLUSIONS: This widespread lack of awareness and inadequate control underscore the need for intensive efforts in these domains. Monitoring is expected to highlight the gaps in the preventive and care services offered to the most vulnerable individuals and it may induce governments and practitioners to address these issues.

Medical care expenditure in suicides from non-illness-related causes.

OBJECTIVES: Several epidemiological studies on medical care utilization prior to suicide have considered the motivation of suicide, but focused on the influence of physical illnesses. Medical care expenditure in suicide completers with non-illness-related causes has not been investigated. METHODS: Suicides motivated by non-illness-related factors were identified using the investigator's note from the National Police Agency, which was then linked to the Health Insurance Review and Assessment data. We investigated the medical care expenditures of cases one year prior to committing suicide and conducted a case-control study using conditional logistic regression analysis after adjusting for age, gender, area of residence, and socioeconomic status. RESULTS: Among the 4515 suicides motivated by non-illness-related causes, medical care expenditures increased in only the last 3 months prior to suicide in the adolescent group. In the younger group, the proportion of total medical expenditure for external injuries was higher than that in the older groups. Conditional logistic regression analysis showed significant associations with being a suicide completer and having a rural residence, low socioeconomic status, and high medical care expenditure. After stratification into the four age groups, a significant positive association with medical care expenditures and being a suicide completer was found in the adolescent and young adult groups, but no significant results were found in the elderly groups for both men and women. CONCLUSIONS: Younger adults who committed suicide motivated by non-illness-related causes had a higher proportion of external injuries and more medical care expenditures than their controls did. This reinforces the notion that suicide prevention strategies for young people with suicidal risk factors are needed.

Assessment of the mode of action for hexavalent chromium-induced lung cancer following inhalation exposures.

Inhalation of hexavalent chromium [Cr(VI)] is associated with increased lung cancer risk among workers in several industries, most notably chromate production workers exposed to high concentrations of Cr(VI) (≥100 µg/m(3)), for which clear exposure-response relationships and respiratory irritation and tissue damage have been reported. Data from this industry are used to assess lung cancer risk associated with environmental and current occupational exposures, occurring at concentrations that are significantly lower. There is considerable uncertainty in the low dose extrapolation of historical occupational epidemiology data to assess risk at current exposures because no published or well recognized mode of action (MOA) for Cr(VI)-induced lung tumors exists. We conducted a MOA analysis for Cr(VI)-induced lung cancer evaluating toxicokinetic and toxicological data in humans and rodents and mechanistic data to assess plausibility, dose-response, and temporal concordance for potential MOAs. Toxicokinetic data support that extracellular reduction of Cr(VI), which limits intracellular absorption of Cr(VI) and Cr(VI)-induced toxicity, can be overwhelmed at high exposure levels. In vivo genotoxicity and mutagenicity data are mostly negative and do not support a mutagenic MOA. Further, both chronic bioassays and the epidemiologic literature support that lung cancer occurs at exposures that cause tissue damage. Based on this MOA analysis, the overall weight of evidence supports a MOA involving deposition and accumulation of particulate chromium in the bifurcations of the lung resulting in exceedance of clearance mechanisms and cellular absorption of Cr(VI). Once inside the cell, reduction of Cr(VI) results in oxidative stress and the formation of Cr ligands. Subsequent protein and DNA damage lead to tissue irritation, inflammation, and cytotoxicity. These effects, concomitant with increased cell proliferation, result in changes to DNA sequences and/or methylation status that can lead to tumorigenesis. This MOA supports the use of non-linear approaches when extrapolating lung cancer risk occurring at high concentration occupational exposures to environmentally-relevant exposures.

Cost-effectiveness of liver cancer screening in adults at high risk for liver cancer in the republic of Korea.

PURPOSE: This study was conducted in order to determine the most cost-effective strategy, in terms of interval and age range, forliver cancer screening in the high-risk population of Korea. MATERIALS AND METHODS: A stochastic modelwas used to simulate the cost-effectiveness ofliver cancer screening by combined ultrasonography and alpha-fetoprotein testing when varying both screening intervals and age ranges. The effectiveness of these screening strategies in the high-risk population was defined as the probability of detecting preclinical liver cancer, and costwas based on the direct cost ofthe screening and confirmative tests. Optimal cost-effectiveness was determined using the incremental cost-effectiveness ratio. RESULTS: Among the 36 alternative strategies, one-year or two-year interval screening for men aged between 50 and 80 years, six-month or one-year interval screening for men aged between 40 and 80 years, and six-month interval screening for men aged between 30 and 80 years were identified as non-dominated strategies. For women, identified non-dominated strategies were: one-year interval screening between age 50 and 65 years, one-year or six-month interval screening between age 50 and 80 years, six-month interval screening between age 40 and 80 years, and six-month interval screening between age 30 and 80 years. CONCLUSION: In Korea, a one-year screening interval for men aged 50 to 80 years would be marginally cost-effective. Further studies should be conducted in order to evaluate effectiveness of liver cancer screening, and compare the cost effectiveness of different liver cancer screening programs with a final outcome indicator such as qualityadjusted life-years or disability-adjusted life-years.

Barriers to cancer screening among medical aid program recipients in the Republic of Korea: a qualitative study.

Few studies have examined reasons why those with low socioeconomic status do not adequately receive cancer screening. We therefore conducted a qualitative study to assess the barriers to cancer screening in people with low socioeconomic status, and to examine the reasons why Medical Aid Program (MAP) recipients do not participate in the National Cancer Screening Program (NCSP). A focus group methodology was used. Participants included MAP recipients (men aged 45-79 years, women aged 35-79 years) who had been invited to cancer screening at least twice based on the NCSP protocol, but had not been screened for any cancer from 2009-2012. We recruited participants living in the cities of Goyang and Paju. A total of 23 MAP recipients participated in four focus group discussions, including 12 men and 11 women. In this qualitative study, we identified six barriers to screening: lack of trust in the NCSP and cancer screening units; fear of being diagnosed with cancer; discomfort or pain from the screening procedure; lack of time, lack of knowledge about cancer screening or lack of awareness of the existence of the NCSP; physical disability or underlying disease; and logistic barriers. Interventions such as individualized counseling, letters and reminders, or other individually-targeted strategies, especially for those with lower socioeconomic status are required to increase participation and reduce disparities in cancer screening.