Clinical Prediction of Pathological Complete Response After Preoperative Chemoradiotherapy for Rectal Cancer

BACKGROUND: The clinical pretreatment factors that accurately predict response to chemoradiation in rectal cancer are not currently known. OBJECTIVE: The aim of this study is to evaluate the clinical factors associated with a pathological complete response after preoperative chemoradiotherapy for rectal cancer. DESIGN: This study is a retrospective review of prospectively collected data. SETTING: This study was conducted at a tertiary care hospital/referral center in South Korea. PATIENTS: From December 2000 to September 2011, a total of 391 consecutive patients with rectal cancer who underwent neoadjuvant chemoradiotherapy followed by radical surgery were identified. The treatment consisted of concurrent chemoradiation, which included preoperative 5-fluorouracil-based chemotherapy and pelvic radiation (median, 5040 cGy); this was followed 8 weeks later (median, 57 days) by surgery with curative intent. MAIN OUTCOME MEASURES: The primary outcome measured was the clinicopathological comparison between pathological complete response (n = 57, 14.6%) and non-pathological complete response (n = 334, 85.4%) groups. RESULTS: The pathological complete response groups had a higher percentage of noncircumferential tumors, nonmacroscopic ulceration, well differentiation, small tumor diameter, early clinical T stage, early clinical N stage, or low levels of pretreatment CEA than the non-pathological complete response group. In multivariate regression analysis, independent predictors of a higher pathological complete response rate were noncircumferentiality (p = 0.007; OR, 3.214), nonmacroscopic ulceration (p = 0.002; OR, 6.702), and low pretreatment CEA level (p = 0.004; OR, 2.656). Significant differences in the pathological complete response rate existed among the 4 risk stratification groups (p < 0.001). For the prediction of pathological complete response by the clinical risk score model, the sensitivity was 64.1% and the specificity was 73.7% (area under the curve, 0.706; p < 0.001). LIMITATIONS: This study was limited because it was a single-institution study with a small sample size. CONCLUSIONS: Pretreatment clinical variables, including tumor circumferentiality, macroscopic ulceration, and CEA level, may be important determinants in achieving a pathological complete response.