Cancer survivors have a 2–6 times higher risk of secondary cancers and recurrence than the general population, particularly survivors of stomach and colorectal cancer, who remain vulnerable to site-specific recurrence and secondary primaries. In Korea, cancer survivors are classified as a high-risk group in the National Cancer Screening Program and are recommended to undergo regular screening; however, evidence on their actual participation and its determinants remains limited. Moreover, potential inequalities in screening by sex, age, socioeconomic status, and health-related factors among cancer survivors have not been comprehensively examined.

This study aimed to determine the cancer screening participation rate among gastric and colorectal cancer survivors using data from the Korea National Health and Nutrition Examination Survey (KNHANES) and examine its association with demographic, socioeconomic, and health-related factors. In addition, to quantify socioeconomic inequalities in screening, the slope index of inequality (SII) and relative index of inequality (RII) were calculated

This study analyzed the 2016–2021 KNHANES data for gastric and colorectal cancer survivors. Cancer screening participation was examined in relation to demographic, socioeconomic, and health-related variables using frequency analysis, Rao–Scott chi-square test, and multivariable logistic regression. Socioeconomic inequalities were quantified using the SII and RII, estimating adjusted odds ratios (aOR) and 95% confidence intervals (CI) per one-step increase in SES. Multicollinearity was assessed using the variance inflation factor (VIF<3), and all analyses were conducted using SAS 9.4 (SAS Institute, Cary, NC, USA).

Gastrointestinal cancer survivors had a 55.3% cancer screening participation rate. The multivariable logistic regression model demonstrated moderate predictive power (c-statistic=0.73). Women (aOR 1.88, 95% CI 1.74–2.04) and older age (aOR 1.05, 95% CI 1.04–1.05) showed higher participation, while unmarried individuals had substantially lower participation (aOR 0.20, 95% CI 0.18–0.23).
Next, among the socioeconomic factors, education level, income level, and marital status showed significant results. As a result of conducting SII/RII analysis to quantify SES inequality, it was found that for each one-step increase in income quintile, the aOR was 1.15 (β=0.14, p<0.001), and for each one-step increase in education level, the aOR was 1.30 (β=0.26, p<0.001). The RII showed that educational inequality (2.19, 95% CI 1.93–2.50) was more pronounced than income inequality (1.52, 95% CI 1.38–1.67).
Health-related factors showed higher participation among those with poor subjective health (aOR 1.24, 95% CI 1.06–1.44), higher EQ-5D scores (aOR 2.74, 95% CI 1.85–4.04), and monthly drinkers (aOR 1.21, 95% CI 1.12–1.30), but lower among current smokers (aOR 0.71, 95% CI 0.65–0.78), hypertensives (aOR 0.82, 95% CI 0.74–0.90), and diabetics (aOR 0.85, 95% CI 0.76–0.95).

Cancer screening participation among survivors was only 50%, with significant disparities by sex, age, education, income, marital status, quality of life, health behaviors, and chronic disease. Uniform management policies are inadequate; targeted interventions are needed for males, low education/income groups, smokers, and those with hypertension or diabetes. As educational inequality (RII=2.19) exceeds income inequality (RII=1.52), customized health education for low-education survivors should be prioritized.