EGFR and cancer prognosis

Abstract

Elevated levels of the epidermal growth factor receptor (EGFR), a growth-factor-receptor tyrosine kinase, and/or its cognate ligands have been identified as a common component of multiple cancer types and appear to promote solid tumour growth. This article examines the relationship between EGFR expression and cancer prognosis based on literature compiled on PubMed between 1985 and September 2000. More than 200 studies were identified that analysed relapse-free-interval or survival data directly in relation to EGFR levels in over 20000 patients. Analysis of the data showed that 10 cancer types both express elevated levels of EGFR relative to normal tissues and have been studied in sufficient depth to allow sound judgements to be made concerning the association between EGFR and patient outlook. The EGFR was found to act as a strong prognostic indicator in head and neck, ovarian, cervical, bladder and oesophageal cancers. In these cancers, increased EGFR expression was associated with reduced recurrence-free or overall survival rates in 70% (52/74) of studies. In gastric, breast, endometrial and colorectal cancers, the EGFR provided more modest prognostic information, correlating to poor survival rates in 52% (13/25) of studies, while in non-small cell lung cancer (NSCLC), EGFR expression only rarely (3/10 studies) related to patient outlook. However, it is likely that the true prognostic significance of the EGFR has been underestimated as the published studies only assessed total cellular EGFR levels, rather than the activated form of the receptor, and were not standardised with regard to patient populations or assay methods. Finally, it is important to stress that failure to detect a prognostic significance for EGFR in any one cancer type does not necessarily preclude patients from benefiting from anti-EGFR therapies.