Background: Recent nationwide studies of disparities in cancer incidence by income are scarce in Korea. This study investigated such disparities in cancer incidence and the stage at cancer diagnosis across income groups in Korea. Methods: This study utilized data from a national cancer database, specifically focusing on cases recorded in the year 2018. Income levels were categorized into quintiles according to the insurance premium paid in addition to the Medicaid benefit. The slope index of inequality (SII) and relative index of inequality (RII) were used to measure absolute and relative differences in cancer incidence by income. A multivariable logistic regression was performed to estimate the risk of a distant stage at cancer diagnosis. Results: The total number of cases of incident cancer was 223,371 (men: 116,320, women: 107,051) with shares of the total of 29.5% (5Q), 20.4% (4Q), 16.0% (3Q), 13.5% (2Q), 15.6% (1Q), and 5% (Medicaid). The most common cancer type was thyroid cancer, followed by gastric and colorectal cancers. The age-standardized incidence rate for all cancers was lowest in the highest income group, but the SII was not statistically significant (SII: −35.7), and the RII was −0.07. Colorectal and cervical cancers had lower incidence rates for higher income groups, while thyroid and prostate cancers had higher incidence rates for higher income groups. The odds ratio for a distant stage at diagnosis for all cancers increased for lower income groups relative to 5Q. Conclusions: Disparities in cancer incidence in a Korean population differed by cancer type, and lower income was a significant predictor of a distant stage at diagnosis for cancers overall. These results emphasize the need for further study of the underlying causes of disparities in cancer incidence and the stage at diagnosis, as well as the need for interventions to mitigate these disparities.
背景：韩国近期关于癌症发病率与收入差异关系的全国性研究较为缺乏。本研究旨在探讨韩国不同收入群体间癌症发病率及诊断分期的差异情况。 方法：本研究采用国家癌症数据库资料，重点分析2018年登记病例。根据医疗保险自付费用及医疗补助受益情况，将收入水平划分为五个等级。采用不平等斜率指数（SII）和相对不平等指数（RII）衡量癌症发病率的绝对与相对收入差异，并运用多变量逻辑回归模型评估癌症诊断时远处转移的风险。 结果：2018年新发癌症病例总数为223,371例（男性116,320例，女性107,051例），各收入组占比分别为：最高收入组29.5%、次高收入组20.4%、中等收入组16.0%、次低收入组13.5%、最低收入组15.6%，医疗补助受益群体占5%。甲状腺癌是最常见的癌症类型，其次为胃癌和结直肠癌。所有癌症的年龄标准化发病率在最高收入组最低，但SII无统计学意义（SII: -35.7），RII为-0.07。结直肠癌和宫颈癌在高收入群体中发病率较低，而甲状腺癌和前列腺癌在高收入群体中发病率较高。与最高收入组相比，低收入群体所有癌症诊断时处于远处转移期的比值比显著升高。 结论：韩国人群癌症发病率的差异因癌症类型而异，低收入是预测癌症诊断时处于远处转移期的重要指标。这些结果强调需要进一步研究癌症发病率及诊断分期差异的根本原因，并制定干预措施以缩小这些差异。
Disparities in Cancer Incidence across Income Levels in South Korea
肿瘤(癌症)患者之家