Femke Doubrava-Simmer, theme Tumours of the digestive tract, published in Gastroenterology that in one third of the cases with more than one site of colorectal cancer (CRC), the different sites are clonally related.
In 5% of colorectal cancer (CRC) patients a second CRC develops, either synchronous or metachronous. In general, these are treated as independent primaries, suggesting these patients have an increased risk for CRC development. Using a combination of molecular techniques we showed that 33% of these multi-focal CRC are actually clonally related, and most likely develop as a result of intraluminal spread. Our results demonstrate that intraluminal spreading of CRC occurs more often than is recognized in daily practice, which affects both diagnostics and treatment of patients with multifocal CRC.