Unresectable metastatic colorectal cancer patient cured with cetuximab-based chemotherapy: a case report with new molecular insights.

Here we report the case of a 20-year-old patient who was diagnosed in 2002 with a metastatic colorectal cancer (CRC). He achieved a complete response under cetuximab-based therapy and remains without disease recurrence until now while chemotherapy was discontinued in 2009. The tumor exhibited high level of epidermal growth factor receptor () amplification, no mutation in , or genes and a microsatellite-stable (MSS) phenotype. Intriguingly this young patient was carrying a monoallelic germline mutation of that was associated with an inactivation of the second allele by loss of heterozygosity on tumor DNA. Moreover, this mutation was associated with a specific mutational signature on tumor level characterized by C > A single base substitutions and a higher mutational load than usually observed in MSS neoplasms. This case report paves the way for further researches on -associated cancers' sensitivity to anticancer therapies.