Trend of Serum CEA in Recurrent Signet Cell Colorectal Adenocarcinomas

Colorectal cancer (CRC) represents a major global health burden, with signet cell adenocarcinoma constituting a rare but aggressive subtype. Despite multimodality treatment with curative intent, recurrence rates remain significant, and outcomes are poor. Carcinoembryonic antigen (CEA) is a widely used biomarker for CRC follow-up; however, its role in signet cell CRC remains inadequately defined. This study aimed to evaluate the trends in serum CEA among baseline CEA secretors and non-secretors presenting with recurrence after curative treatment and assess its value in postoperative surveillance. This retrospective study analyzed data from a prospectively maintained database at a tertiary cancer center between June 2011 and October 2021. Inclusion criteria were patients with recurrent signet cell colorectal adenocarcinoma, treated with curative intent, and with available CEA values at baseline, treatment completion, and recurrence. Variables included demographic data, baseline CEA levels, recurrence patterns, and CEA status at recurrence. Baseline CEA secretors were defined as those with preoperative CEA > 5 ng/ml. Statistical analysis employed chi-square and Fisher's exact tests for categorical data, with significance set at p < 0.05. Out of 263 signet cell colorectal adenocarcinoma patients, 100 recurrent cases were analyzed. Baseline CEA secretors accounted for 35%, while 65% were non-secretors. Elevated CEA levels at recurrence were observed in 94.3% of baseline secretors and 67.7% of non-secretors. Among secretors, only 5.7% showed normal CEA at recurrence. Recurrence patterns revealed no significant correlation with baseline secretor status, though peritoneal recurrences were more frequent among secretors. Most recurrence cases, irrespective of baseline CEA levels, exhibited elevated CEA levels, emphasizing its relevance in surveillance. This study highlights the importance of CEA monitoring in the follow-up of recurrent signet cell colorectal adenocarcinoma. Elevated CEA levels are a reliable marker for recurrence, even in baseline non-secretors. Conversely, normal CEA in secretory patients offers a reassuring prognostic indicator. The study highlights the non-site-specific nature of CEA elevation at recurrence. The study's findings support the continued use of serial CEA measurements in the postoperative surveillance of signet cell CRC.