Tumor Markers Flashcards
1
Q
The Hook effect
A
- a very high concentration of an analyte gives a falsely low result
- high concentration exceeds the binding capacity of both the binding capture antibodies and the signal bearing antibodies preventing their association
- if the sample is sufficiently diluted the assay will give an appropriate result
2
Q
Effect of heterophile antibodies on immunoassays
A
Can cause false positives or false negatives
3
Q
PSA
A
- Annual PSA measurement + digital rectal exam is recommended for men > 50 yo
- Abnormal DRE or PSA > 4 ng/mL is indication for prostate bx
- Recommendation now controversial
- PSA is organ specific but not cancer specific
- May be elevated in
- benign prostatic hyperplasia
- prostatitis
- prostatic infarct
- following needle biopsy
- Only 30-40% of men with elevated PSA have prostate cancer
- There is intraindividual variation and variation according to race, with levels being higher in blacks
- Poor sensitivity; many men with prostate cancer have serum PSA < 4 ng/mL
- Adjunctive PSA indices
- Age specific cutoffs (PSA increases with age)
- PSA density (PSA divided by estimated prostatic volume)
- PSA velocity (rate of change in successive PSA determinations)
- free PSA (lower free PSA fraction correlates with the prostate cancer)
4
Q
Colorectal cancer screening
- testing methods
- false positive results from
- false negative results from
A
- Recommended screening
- fecal occult blood testing
- guaiac based testing: hemoglobin has endogenous peroxidase activity that can oxidize guaiac in the presence of H2O2 to a blue color
- false positive can result from
- NSAIDs
- consumption of heme (in meat)
- consumption of peroxidase (turnips and horseradish)
- false negatives result from excess vitamin C consumption
- immmunohistochemical testing: no dietary restrictions
- flexible sigmoidoscopy
- barium enema
- colonoscopy
- fecal occult blood testing
5
Q
CEA
A
- Increased in some patients with colon cancer
- not recommended for colon cancer screening
- plays a role in preoperative evaluation of patients with known colon cancer and in the postoperative monitoring of such patients
- highpreoperative CEA concentration implies a worse overall outcome
- CEA is elevated in
- 25% of tumors confined to the colon
- 50% with nodal metastasis
- 75% with distant metastases
- CEA may be increased in
- gastric adenocarcinoma
- breast cancer
- lung cancer
- pancreatic adenocarcinoma
- medullary thyroid carcinoma
- cervical adenocarcinoma
- urothelial carcinoma
- Mild CEA elevation can be caused by
- smoking
- peptic ulcer disease
- inflammatory bowel disease
- pancreatitis
- hypothyroidism
- biliary obstruction
- cirrhosis
6
Q
Thyroglobulin
A
- detection of tumor recurrence in differentiated (follicular and papillary) thyroid carcinoma
- antithyroglobulin antibodies are potential sources of interference
7
Q
Cancer antigen (CA) 125
A
- elevated in nonmucinous epithelial ovarian neoplasms
- may be elevated in
- pregnancy
- leiomyomas
- benign ovarian cysts
- pelvic inflammation
- ascites
- endometriosis
- endometrial, Fallopian tube, pancreas, breast, and colon neoplasms
- levels tend to decrease in postmenopausal women
8
Q
CA 27.29 and CA 15-3
A
- CA27.29 (also called BR 27.29) and CA15-3 measure different epitopes of a single antigen-the protein product of the breast cancer associated MUC1 gene
- Both are elevated in 60-70% of women with advanced stage breast cancer
9
Q
CA 19-9
A
- Marker for pancreatic adenocarcinoma; elevated in 80% at presentation
- May be elevated in patients with other malignancies
- hepatobiliary
- gastric
- colorectal
- breast
- May be elevated in
- pancreatitis
- cholestasis
- cholangitis
- cirrhosis
- Not produced by Lewis negative patients
10
Q
AFP
- normally synthesized where?
- elevations in benign states
- marker for what tumors
A
- Normally synthesized in the yolk sac, fetal liver, and fetal GI tract
- Elevated in normal pregnancy, cirrhosis, and hepatitis
- Elevated in yolk sac tumors and most HCC
11
Q
HCG elevated in
A
- pregnancy
- trophoblastic disease
- choriocarcinoma
- 15% of pure seminomas
- rare tumors from other sites (GI tract, GU tract)
12
Q
Beta2 microglobulin
A
- elevated whenever there is increased cell death
- an independent prognostic factor in multiple myeloma
13
Q
Alkaline phosphatase as a tumor marker
A
- An indication of osteoblastic activity
- Elevated in osteogenic sarcoma or bone mets
- Sensitive test for hepatic mets
- Regan isoenzyme may be elevated in a variety of advanced malignancies
14
Q
Markers of carcinoid tumors
A
- Produce serotonin (5 hydroxytryptamine, 5-HT) that is metabolized and excreted in urine as 5 hydroxyindoleacetic acid (5-HIAA)
- Foregut carcinoids produce
- histamine
- catecholamines
- 5-hydroxytryptophan (5-HTP)
- Midgut carcinoids usually make only seratonin
- Hindgut carcinoids are often nonsecretory
- Other peptides that can be produced in excess
- synaptophysin
- neuropeptide K
- pancreatic polypeptide (PP)
- chromogranin A (CGA)
15
Q
Markers of medullary thyroid carcinoma
A
- plasma calcitonin with or without provocative testing with calcium infusion
- serum CEA commonly elevated
