What labs should be ordered for a newly diagnosed sigmoid adenocarcinoma?

Laboratory Tests for Newly Diagnosed Sigmoid Adenocarcinoma

For patients with newly diagnosed sigmoid adenocarcinoma, essential laboratory tests should include complete blood count, liver and renal function tests, and carcinoembryonic antigen (CEA) as the baseline diagnostic workup. 1

Core Laboratory Tests

Blood Tests

• Complete blood count (CBC)
• Liver function tests:
  • Alkaline phosphatase (ALP)
  • Aspartate aminotransferase (AST/SGOT)
  • Alanine aminotransferase (ALT/SGPT)
  • Total bilirubin
• Renal function tests:
  • Blood urea nitrogen (BUN)
  • Creatinine
• Tumor markers:
  • Carcinoembryonic antigen (CEA) - critical baseline marker for monitoring recurrence 1, 2

Rationale for Laboratory Testing

The ESMO guidelines specifically recommend these tests for the initial evaluation of colon cancer patients 1. CEA is particularly important as it serves both diagnostic and prognostic purposes:

• CEA is elevated in approximately 94.6% of patients who develop liver metastases 2
• CEA provides a crucial baseline value for post-treatment monitoring
• CEA is significantly more sensitive than liver function tests alone for detecting metastatic disease 2

Additional Tests to Consider

Based on clinical presentation and initial findings, these additional tests may be warranted:

• Lactate dehydrogenase (LDH) - can be elevated in metastatic disease 1
• Albumin - decreased levels may indicate advanced disease and poor nutritional status
• Coagulation studies (PT/INR) - especially if surgery is planned

Important Clinical Considerations

1. Timing of laboratory tests: All laboratory tests should be completed before initiating treatment to establish baseline values.

2. CEA limitations: While highly sensitive, a normal CEA does not exclude metastatic disease. Approximately 3.3% of patients with liver metastases may have normal CEA and normal liver function tests 2.

3. Follow-up testing: After treatment, CEA should be monitored every 3-6 months for 3 years and every 6-12 months during years 4 and 5 1.

4. Cost-effectiveness: Research suggests that routine liver function tests add minimal value beyond CEA monitoring and could be eliminated from routine follow-up, reducing costs without significantly decreasing diagnostic accuracy 2.

The laboratory evaluation should be performed alongside appropriate imaging studies (CT scan of abdomen/pelvis, chest X-ray or CT) and complete colonoscopy to fully stage the disease and guide treatment decisions 1.