Quantitative dot blot method for measuring EGFR protein levels in patients with colorectal cancer.

PURPOSE: The expression levels of the epidermal growth factor receptor (EGFR) may be associated with the efficacy of cetuximab (CTX); however, conventional immunohistochemical assays lack quantitative accuracy and standardization, thereby making it hard to achieve absolute quantification of protein expression and cross-platform comparisons. To establish an objective quantitative standard for EGFR protein expression levels, we employed quantitative dot blotting (QDB) to analyze tumor samples from patients with RAS/BRAF wild-type colorectal cancer (CRC). MATERIALS AND METHODS: We collected 89 formalin-fixed, paraffin-embedded (FFPE) tumor tissue specimens from patients with CRC stored at Yuhuangding Hospital in Yantai for QDB testing. Of these, 42 served as untreated controls, and 47 patients received CTX treatment. RESULTS: EGFR protein levels in all patients with CRC ranged from 0.05 to 3.85 nmol/g (n = 89). Using the predefined cohort-wide cutoff of 0.23 nmol/g, a chi-square test performed using the Statistical Package for the Social Sciences software revealed that patients with low EGFR expression had longer overall survival, regardless of CTX treatment. CONCLUSIONS: This study established a QDB-based assay capable of quantitatively and objectively measuring EGFR protein levels in CRC specimens. This assay helps establish the value of EGFR protein as a predictive biomarker and is expected to assist in the retrospective and prospective evaluation of anti-EGFR therapies in clinical trials.