Clinical Utility of Serum CA 19-9 Level in Colorectal Carcinoma Patients With Normal Serum Carcinoembryonic Antigen Levels: Correlation With Clinicopathological Features and Survival Outcomes.

Introduction Colorectal cancer (CRC) is a major global health concern and is the third most commonly diagnosed cancer worldwide, accounting for approximately 11% of all cancer cases. It is more common in men than women. While the incidence has been declining among older adults (>65 years), its incidence and case fatality rate have increased (2% and 1.3%, respectively) among those younger than 50 years. The American Society of Clinical Oncology recommends the measurement of carcinoembryonic antigen (CEA) for prognostication and postoperative follow-up in CRC. However, routine checking of the level of carbohydrate antigen 19-9 (CA 19-9) as a marker of colon cancer is not recommended. The problem lies in young patients and poorly differentiated histological varieties where CEA is usually not elevated, especially in earlier stages. Among other existing tumor markers, CA 19-9 is a well-studied marker that is elevated in many abdominal malignancies, especially of hepatobiliary origin. Here, we explored its role in CRC. Objectives Our primary objective was to determine the association between serum CA 19-9 and CRC in patients with a normal CEA value. The secondary objective was to determine the association of serum CA 19-9 level with various clinicopathological features and its impact on short-term survival. Materials and methods This retrospective-prospective observational study was conducted among the patients of the Department of General Surgery, Department of Surgical Oncology, and Department of Surgical Gastroenterology of Medical College and Hospital, Kolkata, West Bengal, India. Statistical analysis was carried out using Microsoft Excel 2019 (Microsoft Corporation, Redmond, WA) and SPSS version 20.0 (IBM Corp., Armonk, NY). Results The study cohort comprised 41 patients with histologically confirmed colorectal carcinoma, including 27 males and 14 females. The age distribution was almost equal (20 vs 21). Twelve patients had stage 1 disease, 9 had stage 2, 14 had stage 3, and 6 had stage 4 disease. The median CEA of all these patients was 3.3, and the median CA 19-9 was 15.1. Elevated serum CA 19-9 levels were significantly associated with poorly differentiated CRC. The median CA 19-9 level increased from stage I (10.0 U/mL) to stage III (29.5 U/mL). Elevated CA 19-9 values were found more often in advanced T categories (T3-T4)' however, the median CA 19-9 value neither correlated with the individual T, N, or M stages nor with the overall disease stages. While there was a trend towards improved survival in node-negative patients, a statistically significant survival advantage was observed in patients with non-metastatic disease. There was also a slight survival advantage in well to moderately differentiated tumors over poorly differentiated varieties (17.27 months vs 15.73 months, respectively), though it was not statistically significant. The overall survival at 18 months follow-up did not change significantly across CA 19-9 levels. Conclusion In colorectal carcinoma patients with normal serum CEA levels, elevated serum CA 19-9 was associated with adverse clinicopathological characteristics, but it does not significantly affect short-term survival. These findings suggest that CA 19-9 may provide complementary clinical information in this selected patient population; however, larger prospective studies with multivariable analyses are needed to clarify its independent prognostic value.