8286923 Social variance in cancer incidence, results from the new Nordic occupational cancer study

<h3>Objective</h3> The updated Nordic Occupational Cancer Study (NOCCA) includes birth cohorts from 1896 to 1980, adds new job categories, and provides 60 years of follow-up from 1961 to 2020. Based on data from 22 million individuals and 4.5 million cancer cases across the Nordic countries, the study offers a unique opportunity to examine both rare and common cancers across a large population. For example, it includes 4,000 cases of mycosis fungoides, and 440,000 cases of lung cancer. The 60 occupational categories can be classified by socioeconomic position (SEP), a key determinant of cancer burden. Individuals in lower SEP-groups have higher rates of smoking-related cancers, while higher SEP-groups show increased incidence of breast, colon, and skin cancers. This presentation highlights breast cancer in women, colon cancer in men, and melanoma in both sexes to illustrate SEP-related disparities. <h3>Methods and Analysis</h3> By combining occupational history with long-term cancer registry data, NOCCA allows for the assessment of cancer risk across specific socioeconomic and occupational groups, including trends over time and between countries. The standardized incidence ratio (SIR), calculated as the ratio of observed to expected cancer cases using rates from the Nordic populations, was estimated. <h3>Results</h3> SIR for breast cancer ranges from 0.89 in the lowest SEP-group to 1.15 in the highest. For colon cancer, the SIR varies from 1.00 to 1.07. In contrast, melanoma shows a wider range, with SIRs spanning from 0.81 to 1.28. <h3>Conclusion</h3> Breast cancer risk increases with socioeconomic position, likely influenced by lifestyle and reproductive factors. Colon cancer shows only a modest variation by SEP, though it may be associated with sedentary occupations. Melanoma presents the strongest SEP gradient, with higher incidence in more advantaged groups, potentially reflecting greater UV exposure. These patterns reveal how socioeconomic factors contribute to variations in cancer risk.