Retrospective characterisation of a Scottish cohort of early-onset colorectal cancer patients

Introduction
Colorectal cancer (CRC) is the fourth most common cancer in the UK, and the second most common cause of cancer-related death. Whilst overall incidence of bowel cancer is stable, early-onset colorectal cancer (EOCRC) – diagnosed under the age of 50 years – has risen by over 50% in the last 30 years. We aimed to characterise our local cohort of EOCRC patients, with a view to identifying areas in which diagnosis could be improved.

Methods
Individuals diagnosed with CRC in NHS Tayside (population ~410,000) between January 2016 and December 2022 were retrospectively identified from our local Cancer Audit dataset. Electronic case note review was conducted on all patients aged less than 50 years at diagnosis to explore patient demographics, mode of diagnosis, stage and survival. Caldicott Guardian approval was granted for this work (IGTCAL-2023-131).

Results
Of the 2,145 CRC cases identified in this period, 105 (4.9%) were diagnosed in patients under the age of 50 years (minimum 20 years, median 45 years). Over half (56.2%) were female, and 68.6% were from less deprived areas (Scottish Index of Multiple Deprivation [SIMD] deciles 6-10). Two-thirds of patients (67.6%) were diagnosed following referral from primary care, and around one in five (19.0%) as a result of emergency presentation to hospital. Sixty-four (61.0%) patients had faecal immunochemical testing (FIT) prior to diagnosis: 95.3% (61/64) were positive (above the 10 μg Hb/g faeces referral threshold), and 76.6% had very high faecal haemoglobin (>400 μg Hb/g faeces). Three-quarters of cancers were left-sided, with rectal (37.1%) and sigmoid (33.3%) the most common sites. Of note, 25.3% of individuals had metastases at presentation, and 52.5% presented at late stage (3 or 4). One-year mortality was 13.3%.

Conclusions
EOCRC accounted for almost 5% of our CRC diagnoses, in keeping with national findings over a similar time period (5.8%). Over 60% had completed a FIT – indicating symptoms/signs and interaction with Primary Care – and the proportion of emergency diagnoses was comparable to that seen for CRC across all ages. Despite this, over a quarter of patients presented with metastatic disease, with associated high mortality. We must gain information on patient experiences en route to diagnosis to identify ways to in which early detection in this group could be improved. Review of referral pathways, assessment of CRC risk, and the role of alternative biomarkers should be considered.