Prognostic Value of Pretreatment Carcinoembryonic Antigen (CEA) in Rectal Cancer Treated with Preoperative Short-Course Radiotherapy with Delayed Surgery or Long-Course Radiotherapy

Purpose: To investigate the prognostic value of the pretreatment serum carcinoembryonic antigen (CEA) level in patients with rectal cancer treated by preoperative short-course radiotherapy (SCRT) followed by chemotherapy and delayed surgery. Patients and Methods: Two hundred and sixty-six consecutive patients with locally advanced rectal adenocarcinoma without distant metastasis receiving preoperative radiotherapy were enrolled. Group 1 patients (n=144) received long-course radiotherapy (LCRT) with 50.4 Gy in 28 fractions using photon radiotherapy (XRT). Group 2 patients (n=122) received SCRT with 25 Gy in 5 fractions using XRT or proton beam therapy (PBT) followed by chemotherapy and delayed surgery. Pathological complete response (pCR), near pathological complete response (npCR), locoregional recurrence (LRR), distant metastasis (DM), disease-specific survival (DSS) and overall survival (OS) rates were estimated and compared to scrutinize the prognostic significance of factors including CEA level. Results: In group 1, higher CEA level (>= 7 ng/mL) was a significant negative prognostic factor of pCR (p = 0.003, OR: 0.133), OS (p = 0.011, HR: 2.999), DM (p = 0.008, HR: 2.569), LRR (p = 0.044, HR: 3.160), and DSS (p = 0.015, HR: 3.273). In group 2, higher CEA level (>= 7 ng/mL) was a significant negative prognostic factor of pCR (p = 0.002, OR: 0.038), OS (p < 0.001, HR: 44.658), DM (p < 0.001, HR: 8.926), LRR (p = 0.028, HR: 8.570), and DSS (p = 0.001, HR: 43.918). The npCR rates for clinical T4 patients were 6.5% and 22.0% (p = 0.032), in group 1 and group 2, respectively. Conclusion: This study elucidates the prognostic merit of the pretreatment serum CEA level in patients with rectal cancer treated by either preoperative LCRT or SCRT followed by chemotherapy and delayed surgery.