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

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. 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. 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. 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.