What is the definition of a tumour marker?
Click to see answer
Definition: A tumour marker is a substance produced by a tumour or by the host in response to a tumour, used to differentiate tumour from normal tissue or to determine its presence.
Click to see question
What is the definition of a tumour marker?
Definition: A tumour marker is a substance produced by a tumour or by the host in response to a tumour, used to differentiate tumour from normal tissue or to determine its presence.
What are the ideal characteristics of a tumour marker?
Ideal characteristics: High sensitivity (detects disease early), high specificity (limited false positives), and usefulness for diagnosis, prognosis, monitoring treatment, and detecting recurrence.
What are the main applications of tumour markers?
Applications: Screening, diagnosis, staging, prognosis, guiding treatment, monitoring therapy response, and detecting recurrence.
Give an example of a tumour marker used for screening and which cancer it screens for.
Screening example: PSA (Prostate-Specific Antigen) is used for screening and detection of prostate disease including prostate cancer.
Which tumour marker is most useful in diagnosing ovarian cancer?
CA‑125 is the most useful tumour marker for ovarian cancer (detected by monoclonal antibody OC125); useful for detecting residual disease following therapy but not recommended for general population screening.
How are tumour markers used in staging cancer?
Staging: Tumour marker levels can help assess extent of disease and tumour burden to complement clinical and imaging staging. Markers may correlate with tumour load and spread.
How are tumour markers used to determine prognosis?
Prognosis: Marker levels (e.g., higher concentrations) often correlate with more advanced disease and worse prognosis—PSA concentration is inversely proportional to survival time in prostate cancer.
How are tumour markers used to monitor treatment? Provide an example.
Monitoring treatment: Serial marker measurements show response to therapy—falling levels indicate response, rising levels suggest progression. Example: AFP and HCG are used to monitor chemotherapy in germ cell tumours.
How do tumour markers help detect recurrence? Give an example.
Detecting recurrence: After curative therapy marker levels should fall to baseline or undetectable; a subsequent rise suggests recurrence. Example: PSA should fall below detection after radical prostatectomy; rising PSA indicates recurrence.
List the major classes of tumour markers.
Classes of tumour markers: Enzymes, hormones, oncofetal antigens/proteins, carbohydrates, blood‑group antigens, other proteins, receptors, and genetic markers.
What are enzyme tumour markers and give an example.
Enzyme markers: Enzymes released or abnormally expressed by tumours (may reflect necrosis or altered membranes). Example: Alkaline Phosphatase (ALP)—elevated in liver disease and osteoblastic bone metastasis.
What is Lactate Dehydrogenase (LD) a marker for?
LD (Lactate Dehydrogenase): A non‑specific enzyme marker elevated in many cancers (e.g., liver cancer, non‑Hodgkin lymphoma, acute leukaemia, testicular cancer, seminoma, neuroblastoma, breast, colon, stomach, and lung cancers). LD5 isoenzyme elevation suggests liver metastases.
What is Prostate Specific Antigen (PSA) and what forms does it exist in?
PSA: An organ‑specific glycoprotein produced by prostate epithelial cells; exists in free and complexed serum forms. It is organ‑specific but not entirely cancer‑specific (can be elevated in benign prostate conditions).
What are hormone tumour markers? Give an example.
Hormone markers: Hormones produced excessively by native tissue or ectopically by tumours. Example: hCG (Human Chorionic Gonadotrophin)—elevated in trophoblastic disease and certain germ‑cell tumours.
What are oncofetal proteins and give an example.
Oncofetal proteins: Proteins produced during fetal life that reappear in malignancy due to gene reactivation. Example: Alpha‑fetoprotein (AFP)—marker for hepatocellular carcinoma and nonseminomatous germ cell tumours.
What are carbohydrate tumour markers? Give two examples and their uses.
Carbohydrate markers: High‑molecular‑weight mucins expressed/secreted by tumours. Examples: CA15‑3 (useful in monitoring metastatic breast cancer) and CA125 (most useful for ovarian cancer monitoring).
What is CA19‑9 and what cancers is it associated with?
CA19‑9: A carbohydrate/blood‑group‑related marker associated with colorectal and pancreatic carcinomas; synthesised by pancreatic and biliary ductal cells.
Which protein markers are used in multiple myeloma and thyroid cancer?
Protein markers: Immunoglobulins (monoclonal proteins) detected on serum electrophoresis are used in multiple myeloma; thyroglobulin is used as a marker for differentiated thyroid cancer (with antithyroglobulin antibodies used for monitoring).
How are receptors used as tumour markers? Provide an example.
Receptors as markers: Hormone receptor status guides therapy and prognosis. Example: Estrogen (ER) and Progesterone (PR) receptors in breast cancer predict response to hormonal therapy and are associated with better prognosis.
What role do genetic markers, oncogenes, and tumour suppressor genes play in cancer markers?
Genetic markers: Alterations in oncogenes (activated proto‑oncogenes) and loss of tumour suppressor genes underlie malignant transformation; these genetic changes can serve as markers for diagnosis, prognosis, and targeted therapy. (See oncogenes and tumour suppressor gene tables.)
