Pretreatment COX-2 protein expression is a predictor of tumor regression in rectal cancer treated with preoperative short-term chemoradiotherapy

Abstract

3610 Background: Neoadjuvant chemoradiotherapy (CRT) followed by total mesorectal excision has become a standard therapy for patients with rectal cancer. However, not all patients have a good response to CRT. Therefore, it is useful to know what the predictor of chemoradiotherapeutic response is. Cumulative evidence has shown that COX-2 has an important role in the progression of colorectal cancer. The aim of this study was to clarify whether pretreatment COX-2 protein expression was a predictor of histopathologic response in patients with rectal cancer treated with preoperative short-term chemoradiotherapy. Methods: Fifty-two patients with lower rectal cancer received short-term preoperative chemoradiotherapy (20 Gy given in 5 daily doses of 4 Gy and administration of Tegafur/Uracil 400mg/day during the same period), followed by total mesorectal excision at National Defense Medical College from 2001 to 2005. COX-2 expression before and after CRT was measured by immunoshistochemistry. The specimens were graded based on the intensity and extent of staining. Tumor regression grading (TRG) was also evaluated (TRG 4, complete regression; TRG 3, regression > 50%; TRG 2, 25% to 50%; TRG 1, < 25%; and TRG 0, no regression). The correlation between COX-2 expression and tumor regression was analyzed. Results: The patient characteristics were as follows: the male:female ratio was 36:16; median age was 62. The Median postoperative follow-up period was 30 months. Two patients had pathological complete response. Good response (TRG 3 + 4) was found in 57.7% of the resected specimens. COX-2 was positive in 80.8% of patients before CRT while in 100% after CRT. The rates of good response (TRG 3 + 4) in patients with and without COX-2 expression were 50% and 90%, respectively (p = 0.021). Conclusions: Patients without pretreatment COX-2 expression were more likely to demonstrate good response to treatment than those with COX-2 expression. Pretreatment COX-2 protein expression can predict response of CRT in patients with rectal cancer. [Table: see text]