OBJECTIVETo explore predictive factors associated with pathologic complete response (pCR) after neoadjuvant chemoradiotherapy for rectal cancer.

METHODSClinicopathological data of 163 patients with locally advanced rectal cancer who were treated with neoadjuvant chemoradiotherapy followed by radical surgical resection from January 2007 to May 2013 were analyzed retrospectively. Univariate analysis and multivariate logistic regression analysis were performed to analyze associated factors of pCR, including age, gender, body mass index (BMI), diabetes, anemia, tumor diameter, distance of the tumor from the anal verge, circumferential extent of the tumor, tumor pathological types, tumor differentiation, pre-chemoradiotherapy T stage, pre-chemoradiotherapy N stage, pre-chemoradiotherapy CEA level, pre-chemoradiotherapy CA199 level, per-operation CEA level, pre-operation CA199 level, radiation dose, chemotherapy modality, time interval from completion of chemoradiotherapy to surgery, etc.

RESULTSTwenty-nine patients(17.8%) achieved pCR after neoadjuvant chemoradiotherapy for rectal cancer. Univariate analysis showed circumferential extent of tumor(≥1/2 cycle)(P=0.018), tumor pathological types(adenocarcinoma)(P=0.036), tumor differentiation (moderate or high)(P=0.021) and pre-chemoradiotherapy CEA level(≤2.5 μg/L)(P=0.007) were significantly correlated with pCR after neoadjuvant chemoradiotherapy for rectal cancer. Logistic regression revealed that circumferential extent of tumor (≥1/2 cycle)(OR=2.901, P=0.020) and pre-chemoradiotherapy CEA level (≤2.5 μg/L)(OR=2.775, P=0.022) were independent predictive factors of pCR after neoadjuvant chemoradiotherapy for rectal cancer.

CONCLUSIONPatients with circumferential extent of tumor ≤1/2 and pre-chemoradiotherapy CEA level ≤2.5 μg/L are more likely to achieve pCR after neoadjuvant chemoradiotherapy for rectal cancer, and these two indices can be used to predict pCR after neoadjuvant chemoradiotherapy for rectal cancer.