EGFR-KRAS genotyping and EGFR-CDX2 expression in sinonasal intestinal type adenocarcinomas: Toward a new targeted therapy?

Abstract

5565 Background: Sinonasal carcinomas are very rare tumors which are sometimes not eligible for curative surgery. Alternative therapies (i.e. conventional chemotherapies/radiotherapy) are used but with poor results. Therefore, the need for a more efficient treatment is mandatory. Aims of our study: Comparing EGFR and KRAS genetic profiles, EGFR and CDX2 phenotypes of sinonasal intestinal type adenocarcinomas (ITAC) with colorectal adenocarcinomas (CRC). Methods: 41 patients were treated in our institution between 1983 and 2007. All pathological specimens were reclassified according to the 2005 WHO classification. An immunohistochemical (IHC) study was carried out for EGFR and CDX2 expression. We were able to analyze 38 of the 41 specimens for KRAS and EGFR mutations. SNaPshot multiplex system was used to determine the presence of the most common mutations which are located in exon 18, 20 and 21 for EGFR and in exon 2 (codon 12 and13) for KRAS. Fragment analysis method was used for EGFR exon 19 deletions. Results: Thirty five of the 38 patients were classified as ITAC (33 men and 2 women). The mean age was 64.5 years. Exposure to wood work was found in 29 cases (85%). CDX2 expression was present in 31 (89%) cases of ITAC and absent in all non intestinal adenocarcinomas (3 cases). EGFR was expressed in 29 ITACs (83%) with various degrees of IHC expression: 19 (56 %) 1+, 7 (21%) 2+, and 3 with 3+ immunopositivity. No EGFR mutation was found in the whole population; 5 ITAC patients (14%) disclosed KRAS mutations. Conclusions: Histological, phenotype and genetic profiles of ITAC are very similar to those of colorectal adenocarcinoma. These results suggest that ITACs with wt KRAS could respond to anti MoAb anti-EGFR therapy in the same way as metastatic CRC. We propose that all sinonasal tumors should undergo: firstly, CDX2 IHC in order to confirm the ITAC histological subtype and then KRAS genotyping to select the wt population which could benefit from such anti EGFR targeted therapy.