Expression of epidermal growth factor receptor as a predictive factor for rectal cancer.

BACKGROUND Expression of epidermal growth factor receptor is observed in 50 - 70% of colorectal carcinomas and is associated with poor prognosis. The objective of this study was to analyze whether epidermal growth factor receptor expression predicts tumor response and sphincter preserving in patients treated with preoperative chemoradiation therapy. METHODS This study was conducted on 34 patients with locally-advanced rectal adenocarcinoma who were treated with preoperative chemoradiation therapy. The patients had histologically-proven adenocarcinoma of the rectum with the inferior margin of the tumor located no farther than 6 cm from the anal verge. Preoperative radiotherapy was delivered to the pelvis with 60CO to 50.4 Gy. All patients received simultaneous chemotherapy with 5-fluorouracil, 300 mg/m(2) IV infused over 24 hr during radiotherapy on days 1 - 5 every week; 28 patients received oxaliplatin 50 - 60 mg/m(2) weekly during radiotherapy. The patients were restaged by physical examination and pelvic CT, between four and six weeks later. Then, they were referred to a surgeon who was expert in gastrointestinal cancer surgery. Subsequently, postsurgical specimen was histopathologically examined and graded according to the Mandard criteria for assessment of pathologic response after neo-adjuvant chemoradiation. Immunohistochemistry for epidermal growth factor receptor was determined at the preradiation biopsy and was evaluated according to the extension and staining intensity. RESULTS Fourteen (41%) out of 34 tumors were epidermal growth factor receptor positive. Twenty (59%) patients responded to pelvic preoperative chemoradiation. Sixteen (47%) patients achieved complete response with no residual tumor in the resected specimen; four (12%) were downstaged (partial response). Response to pelvic radiotherapy was observed in 80% of those negative for epidermal growth factor receptor and in 28% of those with positive epidermal growth factor receptor (P = 0.005). Only two of 14 positive epidermal growth factor receptor patients achieved a complete response, while 14 of 20 of the negative epidermal growth factor receptor patients developed complete response. In our study, the sphincter preservation rate was 43% in positive epidermal growth factor receptor patients and 80% in those who did not express epidermal growth factor receptor (P = 0.036). CONCLUSION Epidermal growth factor receptor expression in the diagnostic biopsy of locally-advanced rectal cancer treated with chemoradiation therapy may serve as an important predictor of complete response to preoperative treatment.