Trends in early-onset cancer incidence rates in the Nordic countries (2003–2022): a population-based study

Background Increasing incidence rates of early-onset cancer at ages 20–49 years have been reported in several countries, especially for colorectal, kidney and breast cancer. We examined recent incidence trends of early-onset cancer in Denmark, Finland, Iceland, Norway, Sweden, Greenland, and the Faroe Islands across 18 major cancer sites and compared to trends at ages 50–84 years. Methods We utilised the NORDCAN database comprising incident cancer cases among individuals aged 20–84 years during 2003–2022. Age-standardised (Nordic population 2000) incidence rates (ASR) per 100,000 person-years were calculated and linear regression applied to the log of ASRs to quantify the estimated annual percent change (EAPC) by age during the 20-year period. Findings Early-onset cancer ASRs increased significantly for 12 of 18 evaluated cancer sites. The largest increases were observed for colon, kidney, and thyroid cancer (EAPCs > 2%), with the highest EAPC observed for colon cancer at <35 years. Increases were also observed for melanoma, multiple myeloma, rectal, prostate, and liver cancer (EAPCs 1–2%). For thyroid cancer, the increases were similar among individuals aged 20–49 and 50–84 years (3.8% vs 4.0%), while for colon and kidney cancer, the increases were higher among individuals aged 20–49 years (colon: 2.7% vs 0.4%; kidney: 2.7% vs 1.2%). In contrast, the increases in melanoma and liver cancer were even greater among those above 50 (melanoma: 2.0% vs 4.2%; liver: 1.5% vs 2.6%). For cancers of the rectum, prostate, corpus uteri, and cervix uteri, the increases in early-onset incidence rates were contrasted by decreasing trends among older individuals. The relative increases translated into 9174 additional early-onset cases (from 47,491 in 2003–2007 to 56,665 in 2018–2022). Interpretation We found evidence of increasing incidence rates of early-onset cancer across 18 major cancer sites in the Nordic countries, especially for colon, kidney, and thyroid cancer. Explanations are likely multi-fold and cancer-specific, including changes in early-in-life risk factor exposures in recent generations and increased diagnostic intensity, in particular for thyroid cancer. Funding Swedish Research Council and Swedish Cancer Society.