- Created by: ellenrobinson
- Created on: 19-05-19 13:21
A tumour marker is a biomarker found in blood, urine, or body tissues that can be elevated by the presence of one or more types of cancer. There are many different tumour markers, each indicative of a particular disease process, and they are used in oncology to help detect the presence of cancer.
There are 3 main types of tumour markers:
- non-specific markers
Examples: ER, PR, AFR, BRACA1
Ideal Tumour Marker
- organ specificity
- only detectable in malignacy
- respond to change in tumour size
Clinical Uses of Tumour Markers
- Tumour staging
- Monitoring the effectiveness of therapy
- Detecting tumour recurrence/ remission
Screening for cancer using tumour markers should increase the early detection of cancer and the long term survival of treated patients and decrease their morbidity.
Prostate-specific antigen present in normal prostate tissue but serum levels tend to be increased in cancer, Prostate cancer is the commonest cancer in men.
PSA screening is found in USA & Canada. Not used in the UK, but death rates from prostate cancer are the same in the USA/Cancer and Uk.
Uk says it's not suitable for a healthy population, false positive and negative results are common.
Very high levels of tumour markers make malignancy likely but the site of the malignancy will not be known.
Structural tumour markers:
- Membrane structural glycoproteins
- Spillover into the circulation into the blood
- Monoclonal antibodies developed against these antigens
Carcinoembryonic antigen (CEA) is a protein found in many types of cells but associated with tumours and the developing fetus. CEA is tested in blood.
The main use of CEA is as a tumour marker, especially with intestinal cancer. The most common cancers that elevate CEA are in the colon and rectum.
Malignancies with increase levels - most common with bowel cancer
Benign diseases with increased levels in association with Hepatitis, Liver disease and smokers.
Uses FOB to provide a positive result which then leads to colonoscopy.
CEA levels are used to monitor blood levels in patients during diagnosis and throughout treatment.
If levels increase then a new treatment is considered.
No tumour marker is used for screening,
CA 15-3 is the best marker used in the early disease.
Treatment for breast cancer:
- oncogene HER2/neu is expressed in some tumours
- HER2/neu measures in tissue and blood samples
- treated with trastuzumab (a monoclonal antibody against HER2/neu)
A section of the lymph node is removed and sent for testing. The patient is kept under anaesthetic. Positive results lead to lymph removal.
Symptoms do not occur in early disease, only 50% with have a raised CA125. Levels of CA125 can be used for monitoring known diseases.
Ovarian cysts can cause an increase in CA125, seen in ultrasound scans.
CA 19-9, is a blood group glycoprotein, 5% of the population do not have a -ve and b -ve blood groups. Malignancies with increase levels, most are pancreatic carcinomas. Benign conditions with increase levels include acute and chronic pancreatitis.
Pancreatic cancer is relatively rare but may also be an increased incidence in those with BRAC1&2 mutation. There is no reliable screening test.
CA 19-9 is used to monitor treatment and recurrence for those who secrete the marker.