Association of pretreatment serum carcinoembryonic antigen levels with chemoradiation-induced downstaging and downsizing of rectal cancer.

The aim of this study was to identify pretreatment clinical parameters associated with preoperative chemoradiotherapy (CRT)-induced downstaging and downsizing of locally advanced rectal cancer (LARC T3-4 or N+). Data from 51 LARC patients, who received preoperative CRT and radical surgery between 2010 and 2013, were retrospectively analyzed. Rectal adenocarcinoma was histologically confirmed in all patients, who ranged in age between 41 and 81 years (median, 64 years). CRT consisted of 50.4 Gy pelvic radiotherapy with concurrent chemotherapy using 5-fluorouracil and leucovorin. After a median interval of 7 weeks post-CRT, the patients underwent total mesorectal excision. Downstaging was defined as the transition from cStage II-III to ypStage 0-I. The longest tumor diameter was measured pre- and post-CRT using computed tomography or magnetic resonance imaging, and based on the surgical specimen, respectively. Downstaging was observed in 16 (31.4%) patients, including 5 (9.8%) with a pathological complete response. The median downsizing rate was 60%. The serum carcinoembryonic antigen (CEA) levels were 0.8-153.9 ng/ml (median, 4.4 ng/ml). The maximum standardized uptake value was 4.7-33.9 (median, 10.8). On univariate analysis, cT stage, tumor size and CEA level were associated with downstaging. On multivariate analysis, only CEA level (≤5 ng/ml) was a significant predictor of downstaging (odds ratio = 16.0; 95% confidence interval: 1.8-146.7; P=0.014). CEA level was the only factor significantly associated with downsizing (>60%) in the univariate analysis. These results demonstrated that pretreatment serum CEA levels are significantly associated with downstaging as well as downsizing of LARC following preoperative CRT. Therefore, this parameter may be useful in personalizing the management of LARC patients.