Tumour Markers Flashcards
What is a tumour marker?
Tumour markers → usually glycoproteins
- Present in body fluids/tissues
- Provide info on presence, progression/remission of tumours
What is the role of a tumour marker?
Diagnosis → risk assessment → screening → patient stratification → monitoring therapy → staging → prognosis → diagnosis
What are the characteristics of an ideal tumour marker?
- High sensitivity & specificity
- Specificity for a single type of cancer
- Correlation of marker level with tumour size
What are the limitations of a tumour marker?
- Most tumour markers do not have sufficient sensitivity or specificity (esp. early stage), to be regarded as diagnostic alone
- Result within RI can’t exclude malignancy or progressive disease
- Raised tumour marker results do not necessarily indicate malignancy, as they may bne increased in benign conditions (CgA)
- With a few exceptions, most tumour markers are not tumour specific and can be associated with more than one tumour type
Give 3 types of tumour markers.
- Hormones
- Enzymes
- Cancer antigen proteins & glycoproteins
What is the marker for thyroid cancer?
Thyroglobulin
What is the marker for pheochromocytoma?
Catecholamines
What is the marker for throphoblastic cancer?
hCG
What is the marker for ovarian cancer?
CA 125
What is the marker for prostate cancer?
PSA
What is the marker for breast cancer?
CA15-3
What is the marker for colorectal cancer?
CEA, CA19-9
What is the marker for hepatocellular cancer?
AFP
(Alpha Fetoprotein)
What is the marker for neuroblastoma?
HVA, VMA
What is the marker for neuroendocrine tumours?
5-HIAA, chromogranin A
What is the marker for colon cancer?
Fecal occult blood
What are the two types of tumour marker testing?
- Immunoassay
- HPLC or HPLC-MS/MS
What are the problems of IA? What is the solution?
- Harmonization
→ perform tests from the same lab using the same method - Heterophile Ab interference
→ dilution study
→ heterophile Ab blocking tube treatment
→ testing using different assay - Biotin interference
→ dilution study
→ test using different assay
→ retest after stoping biotin supplements - Hook effect
→ dilution study
What are the quality requirements of tumour marker tests?
Pre-analytical
- Tubes
- Correct patients
- Storage
Analytical
- Assay performance: precision (reflected by coefficient of variation)
- Quality controls
- Proficiency testing
Post
- Calculation
What are the prostate specific antigens forms?
- PSA complexed with antichymotrypsin (PSA-ACT) → 55-95%
- free PSA (fPSA) → 5-45%
- Total PSA = fPSA + PSA-ACT
What are the total PSA ranges?
0-4 ng/mL = low risk of PCA
4-10 ng/mL = diagnostic gray zone
>10 ng/mL = 40-50% with PCA
When else can AFP be elevated?
Pregnancy, liver disease
