Expression of epidermal growth factor receptor in canine osteosarcoma: association with clinicopathological parameters and prognosis.

Expression of epidermal growth factor receptor (EGFR) is associated with aggressive growth and metastasis of a range of tumours, including osteosarcomas (OS), although some studies have reported no relevance to clinicopathological events or prognosis. The present study evaluated EGFR mRNA and protein expression in a panel of OS cell lines, normal bones, frozen primary OS and tissue microarrays. EGFR expression was significantly elevated in primary OS compared to normal bones and in metastases of OS to the lungs in comparison with extrapulmonary sites. However, there were no clinical or pathological associations with mRNA expression levels in frozen tumours. Tissue microarray analysis demonstrated that a subset of canine OS with high EGFR expression was associated with significantly shorter survival times and disease-free intervals. Cytoplasmic expression of EGFR was present in 75% of metastases and was similar to expression in primary tumours. EGFR expression alone is not a reliable predictor of outcome and other markers are necessary for further prognostic stratification of dogs with OS. However, these findings suggest that a subset of dogs may benefit from anti-EGFR adjuvant therapies.