Purpose: Epidermal growth factor receptor (EGFR) expression is observed in 50%-70% of colorectal carcinomas and is associated with poor prognosis. The aim of this study was to determine the EGFR expression rate in locally advanced rectal cancer and to analyze whether EGFR expression predicts tumor response to preoperative radiotherapy.
Methods and materials: Between December 1997 and October 2000, 45 patients were included. Treatment consisted of preoperative pelvic radiotherapy and, in 21 patients, 2 courses of 5-fluorouracil leucovorin. Surgical resection was performed 4-8 weeks later. Immunohistochemistry for EGFR was determined at the preradiation diagnostic biopsy and in the resected specimens. Immunostaining was performed using EGFR monoclonal antibody (Biogenex, MU 207-UC). Immunohistochemical staining was evaluated according to extension and intensity. We defined positive staining (EGFR+) as extension of 5% or more.
Results: Preoperative treatment resulted in pathologic complete remission in 7 patients (15%), downstaging in 13 patients (29%), and no response in 25 patients (56%). EGFR+ was observed in 29 of 45 tumors (64%) and was associated with neither clinical tumor stage nor clinical nodal stage. The overall response rate was 34% in EGFR+ patients vs. 62% in those who were EGFR- (p = 0.07). Only 1 of the 7 pathologic complete remission patients was EGFR+ (p = 0.003).
Conclusions: EGFR is expressed in a significant number of locally advanced rectal tumors. EGFR expression is an indicator for poor response to preoperative radiotherapy in advanced rectal carcinoma.