510P Young adult colorectal cancer in Southwestern Ireland, 2015-2019

Abstract

The incidence of colorectal cancer (CRC) in younger adults (<50 years) has increased in Europe over the last two decades, presenting unique challenges across the cancer management continuum. This study examined the clinicopathologic variables and outcomes of younger adults diagnosed with CRC in our region over the last 5 years. Cases of invasive adenocarcinoma of the colon or rectum were identified through a prospectively maintained regional pathology database. Patients aged 18 to 50 years old (inclusive), diagnosed between 2015 and 2019, in counties Cork and Kerry, Ireland, were included. Those with familial syndromes or a history of inflammatory bowel disease were excluded. A total of 1709 new CRC diagnoses were identified, 103 of which met the inclusion criteria (7%). The median age was 45 years (range 30-50) and 51% were female. At presentation, 43% (n=41) had stage III and 30% (n=28) stage IV disease, which was greater than the overall population (28% stage III, 20% stage IV). Tumours were predominantly left-sided colon (48%, n=49) and rectal (32%, n=32) as opposed to right-sided (20%, n=20). Molecular studies in stage IV disease revealed mutations in KRAS in 54% (n=26) and BRAF in 7% (n=3). Most patients underwent mismatch repair protein testing (89%, n=92) with the majority intact (99%). The 3-year disease-free survival rate for resected Stage I-III disease was 72% (n=21). The 3-year overall survival rates were 100% (n=11), 94% (n=16) and 25% (n=16) for stages I-II, III and IV, respectively, compared to 92%, 74% and 19% in the overall population. New cases were spread evenly over the time period at approximately 20 per year. The proportion of new CRC diagnoses represented by younger adults has remained stable in Cork and Kerry since 1995 (range 7-8%). A significant number of younger adults with no identifiable genetic or medical predisposition were diagnosed with CRC. Left-sided tumours dominated and younger patients presented with more advanced disease, which has been observed in many high income countries. The proportion of cases represented by younger adults in our region appeared stable over the last two decades, however, this study needs to be expanded nationally to establish if there has been an increased incidence in line with recent international data.