tumour markers Flashcards
what are tumour markers
macromolecules forming part of a malignant cells
measured in blood, urine or tissue samples
used to diagnos cancers
3 main types of tumour markers
structural
secreted/enzymes
non-specific markers of cell turnover/DNA
examples of tumour markers
proteins glycoproteins ocofoeatal antigens receptors hormones enzymes oncogenes tumour supressor genes
what is the ideal tumour marker
100% organ specific and only detectable in malignancy
factors that affect tumour markers
- most normal tissues may produce the fator too
- cell proliferation affects amount of the marker
-amount of blood the tumour is getting - natural excretion of tumour
- variabiluty in assays
tumour markers are COMPLEX
clinical use of tumour markers
monitor effectiveness of therapy
detect tumour recurrence or remission
what is the sensitivity of a tumour marker screening
ability to detect the presence of the disease
% of those with the disease who get a positive result above the ut off, true positive
what is the specificiy of a tumour marker screening
ability to excluse disease
% of those who get a negative result below the cut off, true negative
whats the ideal outcome of tumour marker screening?
- screening for cancers using tumour markers incerases the early deetection and long term survivall of treated patientes and decrease deaths
BUT none of the current available marker are perfect or 100% effective
prostate specific antigen PSA
serine protease present in seminal fluid
increased levels in cancer
is PSA test sensitive?
yes because its present in cancer
but also present in normal but at lower levels
is the PSA test specific
depends where the testing limit is
if its lowered too much it will give false positives eause PSA is found in normal tissue too, need to balance the speficiness
prostate cancer screening
commoness cancr in men
present in lots of deaths subclinically
how effective has prostate screening been?
screening done in US and canada
more patients have been diagnosed and early treatment
BUT death rate still the same
UK havent seen it as effective so havent started screening
what have the Uk dont about prostate screening
not seen ti worth it to screen but hae made people ore aware of it and that those worried about it can recive advice
what are the clinical uses of PSA for prostate cancer
screening: limited to as risk groups
diagnosis: limited to those at risk
prognosis: limited
tumour staging: limited to none
what does a tumour diagnosis depend on?
biopsy and tissue histology
structural tumour marker example
epitheliall cell surface glycoproteins
can spill over into circulation and are detected by monoconal antibodies
CEA
carinoembryonic antigen
found in almost any carcinoma but commonly in bowel cancer
why is CEA not a perfect marker?
its also found in elevated levels in benign diseases
- hepatitis, cirrohis, janudice, bronchitis
screening for bowel cancer?
nationwide for 60-69yrolds
what does the bowel cancer screening look for?
dy reagent strips
testing for haemoglobin/blood
sometimes polyps or bowel cancers bleed so screening is for faecal occult blood
pos results allow for a colonocopy for further investigations
what is used to monitor bowe cancer
CEA
how is CEA used to monitor bowel cancer
used to asses effectiveness of treatment and recurrentce
monitor blood levels throughout treatment allowing effective further treatment or surgery
