Educational differences in cancer incidence, stage at time of diagnosis, and survival in Norway

The study investigates differences in cancer incidence, stage, and survival between municipalities with varying levels of education in Norway. It replicates the design of a similar study conducted in Oslo to assess whether similar patterns are present nationwide.

We used aggregated data from the Cancer Registry of Norway (2014-2023) to calculate age-standardized incidence rates, stage at diagnosis, and five-year relative survival for colon, rectal, lung, melanoma, breast, and prostate cancer across municipalities. Municipalities were grouped by educational level (low, medium, high), and outcomes were compared.

The study included 191,213 cases. Age-standardized incidence rates (per 100,000 person-years) differed significantly by education for all cancer types except breast cancer (p = 0.70). Melanoma and breast cancer incidence was highest in high-education areas (melanoma: 45.2 vs. 36.9; breast: 135.6 vs. 120.3), while lung cancer was highest in low-education areas (64.4 vs. 56.3). Colon, rectal, and prostate showed smaller but significant differences (colon: 54.7 vs. 54.5, p < 0.001; rectal: 24.5 vs. 25.9, p < 0.001; prostate: 189.8 vs. 191.5, p < 0.001). Low-education areas had the highest proportion of distant metastases for most cancers, with significant variation for lung (p = 0.003) and prostate (p < 0.001). Mid- or high-education areas more often had localized disease, except melanoma. Low-education areas had lower five-year relative survival, significant only for breast cancer (p = 0.037).

Cancer incidence, stage, and survival varied between municipalities grouped by inhabitants' educational level. Findings align with those of the Oslo study, highlighting consistent education-related disparities in cancer outcomes nationwide.