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Normalization of Carcinoembryonic Antigen Levels Post-Neoadjuvant Therapy Is a Strong Predictor of Pathologic Complete Response in Rectal Cancer
Ariella Kleiman*1, Nancy Morin1, Philip H. Gordon1, TE Vuong2, Abbas Kezouh3, Julio Faria1, Gabriela Ghitulescu1, Marylise Boutros1
1Surgery, Jewish General Hospital, Montreal, QC, Canada; 2Radiation oncology, Jewish General Hospital, Montreal, QC, Canada; 3Biostatistics and Epidemiology, Jewish General Hospital, Montreal, QC, Canada
PURPOSE: Several authors have investigated the relationship between carcinoembryonic antigen (CEA) and pathologic complete response; however to date there is no clear consensus regarding its predictive value. The purpose of this study is to examine the association of pre-treatment and post-treatment CEA with pathologic complete response.
METHODS: After institutional review board approval, we conducted a retrospective chart review of a prospectively maintained database of all patients who underwent primary rectal cancer resections after having completed neoadjuvant treatment from 1/07 -11/13. Patients were divided into three groups based on final pathology: pathological complete response (PCR), defined as T stage of 0 in the operative specimen, partial response (PR), and no response (NR). Pretreatment CEA was measured at the initial visit with the oncologist or surgeon, while posttreatment CEA was measured after completing neoadjuvant treatment and prior to surgery. In our laboratory, a normal CEA ranges from 0-3.0 ug/L. Chi-square, student's t and wilcoxon rank sum tests were used for univariate analyses for categorical, normally distributed continuous and non-normally distributed continuous variables, respectively. All variables with a p<0.15 on univariate analysis were included in a multivariate logistic regression model.
RESULTS:141 (63 years, 60.4% male) patients underwent primary rectal cancer resections after completing neoadjuvant treatment (56% external beam, 44% brachytherapy). Of those, 28 (19.96%) achieved PCR, 43 (30.5%) had PR, and 69 (48.9%) had NR. Univariate analysis revealed that patients with PCR had similar demographic, pretreatment tumor characteristics, staging, pretreatment CEA levels and CEA ratios (posttreatment/pretreatment). For patients with an initial elevated CEA (n=85, 60%), posttreatment CEA was significantly lower for patients with PCR compared to those with partial or no response (median 2.2 [IQR1.00,2.90] vs median 3.3[IQR1.9,6.3]), p<0.03. On multivariate logistic regression, in patients with an initial elevated pretreatment CEA and taking into account age, gender, poorly differentiated tumors, and smoking status, a normal post-treatment is a highly significant predictor of PCR (OR 59.2 (95%CI 1.66,∞).
CONCLUSIONS: In patients with an initially elevated CEA, a normal post- neoadjuvant treatment CEA is a highly significant predictor of pathologic complete response.
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