Early-onset cancers are often defined as diagnoses below 50 years of age. Cancer incidence in this age group increases for specific cancer sites according to several international publications. This study describes the cancer incidence trends in Belgium in 2004–2020 in 20–49-year-old people. Overall cancer incidence increases by 0.3% per year in this age group. A decrease is observed for several cancers, including breast, prostate and lung cancer. On the other hand, the risk of being diagnosed with, e.g. melanoma, testicular cancer and thyroid cancer increases. Besides describing incidence trends in young and middle-aged adults, this study demonstrates that data from other (high-income) countries do not necessarily reflect the situation in Belgium and highlights the importance of national population-based data from cancer registries.

(Belg J Med Oncol 2023;17(6):230–5)