Demographic and Clinical Characteristics of Early-Onset Colorectal Cancer in Sweden and Finland: A Multicentre Retrospective Cohort Study Over Three Decades.

Colorectal cancer is the third most common cancer worldwide, and the proportion of individuals diagnosed under the age of 50 years, referred to as early-onset colorectal cancer (EOCRC), is increasing. The aim of this study was to evaluate how the demographic and clinical features of EOCR in northern Sweden and Finland have changed over time. All patient data were extracted from local hospital surgical department databases between 1995 and 2022. Two CRC cohorts, Study Cohort I (1995-2005) 1237 patients and Study Cohort II (2006-2022) 4526 patients, were compared for age, sex, disease stage, tumour grade, tumour location, and mismatch repair status. EOCRC patients comprised 7% of all CRCs in Study Cohort I and 4% in Study Cohort II. The mean ages were 42 and 43 years respectively, and 55% of patients were female. The vast part of EOCRC tumours were left-sided stage III-IV cancers. Most tumours (n = 204, 73%) were low grade, and 10% showed mismatch repair deficiency. No significant differences in demographic or tumour characteristics were seen over time. EOCRC in northern Sweden and Finland is characterised by advanced-stage, low tumour grade, a slight female predominance, and stable clinical and pathological features. These findings partly contrast with reports on EOCRC from other high-income countries, highlighting the need for further research on advanced molecular characteristics and potential gender differences in incidence and survival of this population.