# Diagnosis of Relapse of Colorectal Adenocarcinoma through CEA Fluctuation

## TL;DR

This study explores whether small changes in CEA levels can predict colorectal cancer relapse before clinical symptoms appear.

## Contribution

The novel threshold of 1.1 ng/mL CEA increase within normal range is proposed as an early indicator of cancer recurrence.

## Key findings

- A CEA increase of at least 1.1 ng/mL predicted recurrence in 23% of patients, up to 8 months before clinical relapse.
- CEA fluctuations were linked to recurrence, chemotherapy, or benign conditions in 79.4% of cases.
- 43.6% of patients showed CEA fluctuations of at least 1.1 ng/mL during follow-up.

## Abstract

Carcinoembryonic antigen(CEA) is a routine marker employed for follow-up of colorectal tumors. We aimed to determine whether a CEA increase within the normal range can be linked to a risk of recurrence. From the period of 2006–2013 we selected 78 consecutive patients with colorectal cancer, who underwent curative surgery with or without neo-/adjuvant chemo- or radiotherapy and had proper follow-up procedures. For analyzing CEA fluctuation, we used the smallest value of the CEA during follow-up as the reference. With the aid of a Chi-squared test, we have chosen the value of 1.1 ng/mL for significant CEA fluctuation. A total of 43.6% of patients had fluctuations in CEA of at least 1.1 ng/mL, with or without increases above 5 ng/mL. From these, in 79.4% of patients, the increases in CEA were explained either by recurrence (44.1%), adjuvant chemotherapy (20.6%) or benign pathology (14.7%). In 23% of the recurrences, a CEA increase of at least 1.1 ng/mL, but below 5 ng/mL, preceded the clinical relapse by a median of 8 months. Our conclusion is that an increase in CEA levels by at least 1.1 ng/mL within the normal range after curative treatment for colorectal cancer may serve as an early indicator of relapse or could be associated with other pathological conditions.