We tested the usefulness of epidermal growth factor receptor (EGFR) immunostaining in primary colorectal adenocarcinoma as a predictor for EGFR status of tumor recurrences in 33 primary tumors and distant recurrences (July 1994 to June 2005). Representative primary and recurrent tumor sections were stained using mouse anti-EGFR antibodies, and only membranous staining of malignant cells was recorded. Results were reported as negative (no staining), 1+ (positivity in <50% of cells), or 2+ (positivity in >50% of cells). Of 33 cases, 19 (58%) showed the same extent of immunopositivity in primary and recurrent tumors. Bivariate logistic regression analysis of primary tumors with 2+ vs those with negative or 1+ staining showed that the primary tumor status had a major predictive relationship with that of recurrence (odds ratio, 45.99; confidence limit, 4.0-524.9; P = .0021). The difference between the median time to recurrence of primary tumors with the various degrees of staining was not statistically significant. Our reporting method provides a useful correlation between the staining profiles of primary colorectal adenocarcinoma and recurrent disease. It is exceptionally reliable in predicting immunopositivity of a recurrence when more than 50% of cells of the primary tumor are immunoreactive.
- Colorectal cancer
- Epidermal growth factor receptor
- Targeted therapy