Question
A 62-year-old patient who underwent surgery for bowel malignancy is being followed up in clinic. Which of the following blood markers is most appropriate for tracking disease progression or recurrence?
CA-125
Serum carcinoembryonic antigen
Alpha-fetoprotein
CA 19-9
CA 27-29
Answer
Serum carcinoembryonic antigen
Detailed Explanation
Carcinoembryonic antigen (CEA) is the most widely used tumour marker in colorectal cancer. It is not suitable for screening or diagnosis due to limited sensitivity and specificity, but it is extremely useful in monitoring disease after treatment.
Key uses of CEA in colorectal cancer:
- Detect post-operative recurrence
- Monitor response to chemotherapy in metastatic disease
- Rising levels suggest tumour progression or relapse
Why others are incorrect:
- CA-125 → ovarian cancer
- AFP (alpha-fetoprotein) → hepatocellular carcinoma, germ cell tumours
- CA 19-9 → pancreatic cancer
- CA 27-29 (similar to CA 15-3) → breast cancer
Important concept:
CEA should always be interpreted trend-wise, not as a single value.
Cheat Sheet (Exam Gold 🔥)
- Colorectal cancer marker = CEA
- Not for diagnosis → ONLY for monitoring
- Uses:
- Post-op surveillance
- Detect recurrence
- Monitor chemotherapy response
- Rising CEA = suspect recurrence/metastasis
- Always compare serial values
Flashcards
Q1. What tumour marker is used in colorectal cancer follow-up?
A: Carcinoembryonic antigen (CEA)
Explanation: Best for monitoring recurrence and treatment response.
Q2. Is CEA useful for screening colorectal cancer?
A: No
Explanation: Low sensitivity and specificity.
Q3. What does a rising CEA level indicate?
A: Possible recurrence or progression
Explanation: Trend is more important than absolute value.
Q4. Which marker is associated with pancreatic cancer?
A: CA 19-9
Explanation: Used for monitoring pancreatic malignancy.
Q5. Which tumour marker is used in hepatocellular carcinoma?
A: Alpha-fetoprotein (AFP)
Explanation: Also elevated in germ cell tumours.
MCQs (High-Level)
MCQ 1
A patient treated for colorectal carcinoma shows a progressive rise in a tumour marker over 3 months. Which is the most likely explanation?
a. Liver regeneration
b. Tumour recurrence
c. Acute infection
d. Vitamin deficiency
Answer: b. Tumour recurrence
Explanation: Rising CEA levels after treatment strongly suggest recurrence or metastasis.
MCQ 2
Which of the following tumour markers is LEAST useful in colorectal cancer monitoring?
a. CA 19-9
b. CEA
c. Serial imaging
d. Clinical examination
Answer: a. CA 19-9
Explanation: CA 19-9 is mainly used in pancreatic cancer; CEA is preferred in CRC.
MCQ 3 (False statement)
Regarding CEA in colorectal cancer, which is FALSE?
a. It is useful for screening
b. It is useful for monitoring recurrence
c. It can assess treatment response
d. Serial measurements are important
Answer: a. It is useful for screening
Explanation: CEA is NOT used for screening due to poor sensitivity/specificity.
MCQ 4
Which tumour marker is most specific for monitoring colorectal cancer post-surgery?
a. AFP
b. CA-125
c. CEA
d. PSA
Answer: c. CEA
Explanation: Standard marker for CRC follow-up.
MCQ 5
A patient with metastatic colorectal cancer is started on chemotherapy. Which parameter is best to assess treatment response?
a. Single CEA value
b. Serial CEA levels
c. CA-125
d. AFP
Answer: b. Serial CEA levels
Explanation: Trend monitoring is key; single values are unreliable.
MCQ 6
Which of the following cancers is most strongly associated with CA 19-9 elevation?
a. Colon cancer
b. Breast cancer
c. Pancreatic cancer
d. Lung cancer
Answer: c. Pancreatic cancer
Explanation: CA 19-9 is the primary marker for pancreatic malignancy.
Summary for Quick Exam Revision
Carcinoembryonic antigen (CEA) is the key tumour marker used in colorectal cancer, primarily for monitoring rather than diagnosis or screening. It is particularly valuable in detecting post-operative recurrence and assessing response to chemotherapy in metastatic disease. A rising trend in CEA levels is clinically significant and should prompt further evaluation for recurrence or progression. Other tumour markers such as CA-125, AFP, CA 19-9, and CA 15-3 are associated with ovarian, liver, pancreatic, and breast cancers respectively, and are not appropriate for colorectal cancer monitoring. Screening for colorectal cancer relies on tools like the Faecal Immunochemical Test (FIT), not tumour markers. Always interpret CEA values in a serial trend rather than as isolated readings, as this provides the most clinically meaningful information.