CRC in young patients is uncommon and a phenotypically more aggressive disease. We completed a retrospective descriptive study to determine epidemiological and pathological characteristics of young patients seen by medical oncology within the Sydney West Cancer Network between 2006 and 2015.
Patients less than 30 years of age with histologically proven CRC were included. Demographic and pathological factors were identified. Extended RAS and BRAF mutation testing was performed for all available tumours.
Thirty patients were included in this study with median age of diagnosis at 26 years (range 15-29). The majority of primary tumours were left sided (63%) with rectum and splenic flexure being the most common sites (30% and 33% respectively). Twenty-four patients (80%) presented with stage 3 and 4 disease and the most common tumour histopathology was adenocarcinoma no special type (26%). Nine patients had MMR staining patterns suggestive of microsatellite instability and 8 of these underwent further genetic testing. Of those tested, 4 were positive for a genetic pre-disposing condition (3 with Lynch syndrome and 1 with sessile serrated polyposis syndrome). There were no familial adenomatous polyposis cases identified. KRAS testing was performed on 29 tumour samples, of which 7 were KRAS mutant (24%). NRAS and BRAF testing was performed on 27 samples and 2 returned mutant for NRAS (7%). No BRAF mutations were identified.
This Australian cohort of patients with CRC is one of the youngest described in the literature. They demonstrated similar clinicopathological characteristics compared to previous studies, including a low incidence of RAS mutations. These features are distinctly different to those seen in classic CRC seen in older patients. The aggressive behaviour of these tumours warrants further exploration of causative factors and therapeutic options.
RAS testing funded by Merck Serono research grant.