Relations of carcinoembryonic antigen (CEA) staining of cancer tissue and serum CEA levels to histologic response in patients with locally advanced rectal cancer (LARC) who received neoadjuvant chemoradiotherapy (nCRT).

Abstract

790 Background: Neoadjuvant chemoradiotherapy (nCRT) is a standard of care for LARC. The serum CEA level is a predictor of the response to nCRT; however, the relation between CEA production immunohistochemically evaluated in cancer tissue and treatment response remains unclear. Methods: The study group comprised 145 patients with clinical Stage II/III rectal cancer who received nCRT followed by surgery from 2005 through 2013. The radiation dose was 40 to 45 Gy. UFT- or S-1-based chemotherapy was given concurrently. Surgery was performed 6 to 8 weeks after the completion of radiotherapy. Immunohistological CEA staining patterns in biopsy tissue obtained before nCRT were evaluated. Specimens in which the luminal cell membrane or the cytoplasm was strongly stained were defined as staining positive. The histologic response was evaluated on the basis of the pathological complete response (ypCR) rate, T downstaging, tumor regression grade (TRG), and tumor shrinkage rate on MRI. Results: CEA staining in biopsy specimens and serum CEA levels were both negative in 17 patients (11.7%) and both positive in 72 patients (49.7%). There was no relation between the groups (p = 0.174). In patients with negative CEA staining, the rates of ypCR, T downstaging, marked regression, and mean tumor shrinkage were 24.3%, 51.4%, 45.9%, and 72.3%, respectively. In patients with positive CEA staining, these rates were 11.1%, 48.1%, 37.0%, and 72.8%, respectively. CEA staining of cancer tissue was not significantly related to the ypCR rate, T downstaging, a marked regression rate, or the tumor shrinkage rate on MRI (p = 0.060, p = 0.849, p = 0.436, and p = 0.874, respectively). Patients with negative serum CEA levels before nCRT had significantly higher rates of ypCR, T downstaging, marked regression, and tumor shrinkage on MRI than did patients with positive serum CEA levels (p = 0.014, p = 0.006, p = 0.002, and p = 0.014, respectively). Conclusions: Serum CEA levels before nCRT were a significant predictor of the histologic response to nCRT; in contrast, tissue CEA staining before nCRT was unrelated to the histologic response to nCRT.