Purpose: Epidermal growth factor receptor-overexpression reported in colorectal cancer, justifies therapeutic use of EGFR-inhibitors. We have recently conducted a phase II study in 57 patients with EGFR-positive advanced colorectal cancer (ACC) who received gefitinib-FOLFOX6 followed by gefitinib-single agent as maintenance. Main biological objective was to assess sEGFR as surrogate marker of tyrosine kinase inhibition and as predictor of response.
Methods: sEGFR, evaluated by quantitative ELISA, was investigated as predictive factor both taking into account the basal value only, and its whole pattern over time. sEGFR was collected at baseline and at every 2-months assessment in 42 cases. Thirty-three patients reported CR/PR as best objective response (BOR), while nine showed SD/PD.
Results: Retrospectively, on average, the sEGFR values reported by both responders (CR/PR) and not responders (SD/PD) were already different at baseline (49.4 +/- 6.2 and 42.4 +/- 8.4 ng/ml respectively). This difference was statistically significant (p = 0.042). Although sEGFR trend over time confirmed the basal difference (p = 0.032), this result should be taken with caution, due to the small number of patients reporting EGFR values besides the basal one.
Conclusions: Higher sEGFR at baseline was associated to BOR and may be considered a significant predictor of outcome in patients with ACC.