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

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.

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.

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).

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.

Swedish Research Council and Swedish Cancer Society.