Objective To explore the predictive factors of tumor regression grade (TRG) of locally advanced rectal cancer treated with neoadjuvant chemoradiotherapy to reduce the risk of overtreatment or insufficient treatment, and provide a basis for individualized treatment for locally advanced rectal cancer patients.

Methods The clinical, imaging, pathological and laboratory data of 52 locally advanced rectal cancer patients treated with neoadjuvant chemoradiotherapy combined with surgical treatment were retrospectively analyzed. The efficacy of neoadjuvant chemoradiotherapy was evaluated by TRG. Univariate χ² analysis and multivariate logistic regression analysis were used to evaluate the correlation between gender, age, tumor stage, serum markers CEA, CA199, distance from lower tumor margin to anal margin, neoadjuvant chemotherapy regimen, and interval between radiotherapy and surgery and tumor regression.

Results For TRG, 8 patients with TRG0 grade (15.4%), 7 patients with TRG1 grade (13.5%), 19 patients with TRG2 grade (36.5%) and 18 patients with TRG3 grade (34.6%) were found. There were 15 cases with good tumor regression (TRG0 + 1 grade), with an incidence rate of 28.9%; while 37 cases (TRG2 + 3 grade) with no significant tumor regression were identified, with an incidence rate of 71.1%. The results of univariate χ² test showed that the distance from the lower tumor margin to the anal margin (χ² = 4.3, P = 0.04) and CEA level (χ² = 5.02, P = 0.03) were the predictive factors of TRG level of locally advanced rectal cancer treated with neoadjuvant chemoradiotherapy. The results of multivariate logistic regression analysis showed that the CEA level was an independent predictor of TRG level of locally advanced rectal cancer treated with neoadjuvant chemoraotherapy (P = 0.03, OR = 0.084, 95%CI: 0.010-0.729).

Conclusions The CEA level is an independent predictor of TRG level of rectal cancer patients treated with neoadjuvant chemoraotherapy.