tumor markers

uncontrolled growth of cells that often forms a solid mass or tumor that may spread to other areas of the body. stages 1- 4

• Substances found in abnormally high concentrations in body fluids or tissues from cancer patients. • can be produced by a variety of different tumors • Few are organ-specific or specific for one type of malignancy • Can be produced directly by the tumor or as an effect of the tumor on healthy tissue. • Bence Jones protein in urine of multiple myeloma patients was first tumor marker identified (1847)

• Detectable in a given malignancy and absent in healthy populations ( sensitivity & specificity ) • Readily detectable in body fluids • Present at concentrations proportional to tumor burden • Conveniently measured by a readily available, simple, reproducible, and inexpensive procedure. • Beneficial to clinical care with a measurable effect on patient outcome.

screening - biopsy indication diagnosis - highlevels indicate disease prognosis - high levels indicate poor prognosis Monitoring treament - monitor efficacy ( see if levels are decreasing ) detection of reoccurrence - increase associated with relapse

• High clinical sensitivity and specificity are required***** • Example of population screening: Fecal occult blood testing for colorectal cancer • No tumor markers identified to date can effectively screen asymptomatic patients. • Most tumor markers currently used are also found in normal cells and benign conditions as well. • Would lead to false positive results, undue alarm, unnecessary procedures • Screening for susceptibility of certain cancers (breast, ovarian, colon) in those with a family history can be done using molecular diagnostics. • Germ-line mutations are identified - Example: BRCA1 and BRCA2 mutations for breast and ovarian cancers

• High levels of tumor marker can be indicative of disease. • High clinical sensitivity and specificity are again important.***** - Cannot use a cutoff value for a tumor marker if healthy individuals can also have high values or if individuals that have cancer can fall below the cutoff level. - Most used in conjunction with symptoms, history, biopsies, ultrasounds, etc. • Example of a diagnostic aid in high-risk groups: • AFP (alpha fetal protein) testing as an addition to ultrasound for hepatocellular carcinoma (HCC) - Used with patients who have cirrhosis who are at high risk of developing HCC

• High levels generally associated with poor prognosis. * Concentrations increase with progression of tumor. * Levels are highest when tumors metastasize. • The presence or absence of a tumor marker may also be valuable and may be used to select chemotherapeutic treatment.

• One of most common and useful applications • Monitoring therapy efficacy • Detecting disease recurrence • After treatment (surgical resection, radiation, drug therapy) tumor markers are often tested serially. -Effective treatment will see a decrease or disappearance of the tumor marker • Blood samples are easy to obtain to detect recurrence versus invasive procedures -Levels of tumor markers in blood often rise before tumor can be detected by physical methods.

Specimen Timing • Timing not critical - no evidence of diurnal variation for most markers • Pretreatment specimen should be taken - can help interpret subsequent results( get a baseline level before treatment) • Specimen should be taken prior to certain procedures that will transiently release tumor markers into circulation Ex. Colonoscopies, abdominal surgeries, prostate biopsies Specimen Handling • Serum or plasma appropriate for most measurements • Gel tubes not suitable for some assays

• Size and variability of tumor marker concentration between different manufacturers • Hard to compare patient results if different assays are used • Wide range of concentrations encountered • Accurate measurement can be challenging • Ex. hCG can range between 10 and 10,000,000 mIU/mL

• Immunoassay • High-Performance Liquid Chromatography • Immunohistochemistry and Immunofluorescence • Enzyme Assays

• Most common method to measure tumor markers - Can be automated, easy to use • Considerations with immunoassays include: linearity, hook effect, and heterophile antibodies

• If a sample exceeds the linear range, samples must be diluted to determine values within the reportable linear range. • Risk of error if performing manual dilutions (have another tech review to reduce risk) • Very high concentrations can lead to antigen excess (hook effect)

• Analyte concentrations exceed the analytical range by a large amount. • Tumor marker concentrations will be grossly underestimated. • Typically only affects sandwich-type immunoassays. • If tumor marker is expected to be higher than reported, dilute sample and repeat testing. - Higher results will be obtained on the dilution if hook effect is present

• Circulating antibodies against human or animal immunoglobulin reagents( HAMA) • Leads to false positive results (occasionally false negative) • Perform dilutions to confirm heterophile antibodies are present - Diluted samples will not give linear results if heterophile antibodies are present

• Potential for carryover with high levels of tumor marker analytes • Can lead to falsely elevated levels in patients - Adequate wash steps can help prevent this

• Used to detect catecholamine metabolites ( hormone made by adrenal glands) in plasma and urine. - Analytes of interest are separated from plasma or urine and introduced to a column where separation by physical characteristics takes place. (charge, size, polarity) • Used to help diagnose: • Carcinoid tumors • Pheochromocytomas • Neuroblastomas • Not subject to hook effect and heterophile antibodies • More labor intensive, more skill required

• Specific antibodies are incubated with tissue sections to detect the presence of antigens using colorimetric or fluorescent secondary antibodies. • Specimens usually obtained through biopsy or fine-needle aspiration. • Example of use: • Estrogen and progesterone receptors in breast cancer - If positive for estrogen and progesterone receptors - respond to hormonal therapy - If lacking receptors - treatment with other chemotherapeutic agents

• Detection of elevations of circulating enzymes can help identify a specific tumor or site of tumor. • Dying cells undergo changes in membrane permeability and release enzymes into circulation. • Examples: • Alkaline phosphatase (ALP) - bone, liver, leukemia, sarcoma • Lactate dehydrogenase (LD) - liver, lymphomas, leukemia

Tumor markers include a wide variety of diverse molecules: • Serum proteins • Oncofetal antigens - Proteins typically found during fetal development but that are found in adults with certain cancers • Hormones • Metabolites • Receptors • Enzymes

• Can be elevated nonspecifically in tumors. - Increased due to high metabolic demand of proliferative cells • Levels correlate well to tumor burden (# of cancer cells, size of tumor, etc.) - Useful to monitor success of therapy

• Multiple Myeloma - Immunoglobulins provide specific measure of plasma cell production of monoclonal proteins

• Hormones and hormone metabolites are used as markers of secreting tumors. • Useful for diagnosing: • Neuroblastomas • Pituitary adenomas • Adrenal adenomas

Best used for monitoring treatment of tumors