Tumour Markers

Question 1

What is a tumour marker?

Answer 1

Tumour markers → usually glycoproteins
- Present in body fluids/tissues
- Provide info on presence, progression/remission of tumours

Question 2

What is the role of a tumour marker?

Answer 2

Diagnosis → risk assessment → screening → patient stratification → monitoring therapy → staging → prognosis → diagnosis

Question 3

What are the characteristics of an ideal tumour marker?

Answer 3

1. High sensitivity & specificity
2. Specificity for a single type of cancer
3. Correlation of marker level with tumour size

Question 4

What are the limitations of a tumour marker?

Answer 4

1. Most tumour markers do not have sufficient sensitivity or specificity (esp. early stage), to be regarded as diagnostic alone
2. Result within RI can’t exclude malignancy or progressive disease
3. Raised tumour marker results do not necessarily indicate malignancy, as they may bne increased in benign conditions (CgA)
4. With a few exceptions, most tumour markers are not tumour specific and can be associated with more than one tumour type

Question 5

Give 3 types of tumour markers.

Answer 5

1. Hormones
2. Enzymes
3. Cancer antigen proteins & glycoproteins

Question 6

What is the marker for thyroid cancer?

Answer 6

Thyroglobulin

Question 7

What is the marker for pheochromocytoma?

Answer 7

Catecholamines

Question 8

What is the marker for throphoblastic cancer?

Answer 8

hCG

Question 9

What is the marker for ovarian cancer?

Answer 9

CA 125

Question 10

What is the marker for prostate cancer?

Answer 10

PSA

Question 11

What is the marker for breast cancer?

Answer 11

CA15-3

Question 12

What is the marker for colorectal cancer?

Answer 12

CEA, CA19-9

Question 13

What is the marker for hepatocellular cancer?

Answer 13

AFP
(Alpha Fetoprotein)

Question 14

What is the marker for neuroblastoma?

Answer 14

HVA, VMA

Question 15

What is the marker for neuroendocrine tumours?

Answer 15

5-HIAA, chromogranin A

Question 16

What is the marker for colon cancer?

Answer 16

Fecal occult blood

Question 17

What are the two types of tumour marker testing?

Answer 17

1. Immunoassay
2. HPLC or HPLC-MS/MS

Question 18

What are the problems of IA? What is the solution?

Answer 18

1. Harmonization
   → perform tests from the same lab using the same method
2. Heterophile Ab interference
   → dilution study
   → heterophile Ab blocking tube treatment
   → testing using different assay
3. Biotin interference
   → dilution study
   → test using different assay
   → retest after stoping biotin supplements
4. Hook effect
   → dilution study

Question 19

What are the quality requirements of tumour marker tests?

Answer 19

Pre-analytical
- Tubes
- Correct patients
- Storage

Analytical
- Assay performance: precision (reflected by coefficient of variation)
- Quality controls
- Proficiency testing

Post
- Calculation

Question 20

What are the prostate specific antigens forms?

Answer 20

• PSA complexed with antichymotrypsin (PSA-ACT) → 55-95%
• free PSA (fPSA) → 5-45%
• Total PSA = fPSA + PSA-ACT

Question 21

What are the total PSA ranges?

Answer 21

0-4 ng/mL = low risk of PCA
4-10 ng/mL = diagnostic gray zone
>10 ng/mL = 40-50% with PCA

Question 22

When else can AFP be elevated?

Answer 22

Pregnancy, liver disease