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Cytologic tumor markers are tumor-specific substances in
the blood serum or other tissues that can assist in determining
the presence or absence of cancer. They can help determine
the initial tumor burden in both the primary site and distant
sites. Tumor markers can be helpful in monitoring for recurrence.
Care should be taken to seek tumor marker information to assist
in determining stage.
The most common tumor markers used for prognosis in breast
cancer are the estrogen receptor assay (ERA) and the progesterone
receptor assay (PRA). Both are steroid hormones receptors.
ERA and PRA are used to estimate the potential response to
endocrine, or hormone, therapy. They help in the determination
of prognosis and the management of breast cancer patients.
Pieces of breast cancer tissue are analyzed in the laboratory
to determine the ERA and PRA. The presence of estrogen and/or
progesterone receptors denotes whether the cancer is growing
in the presence of either or both naturally occurring hormones.
Cancer antigen 15-3 (CA-15-3), a tumor associated glycoprotein,
is found in the serum. It can be useful in monitoring the
presence of metastatic breast cancer and the patient's response
to chemotherapy.
Prostate-specific antigen (PSA), a proteolytic enzyme, is
used as a screening mechanism for prostate cancer. It can
monitor the presence of metastatic disease in patients who
have undergone a radical prostatectomy. PSA is not effective
for mass screenings because elevated PSAs can also be found
in aging patients and in association with benign prostatic
hypertrophy (BPH) and prostatitis.
One oncofetal antigen, carcinoembryonic antigen (CEA), has
been used for many years to monitor colon, lung, breast, and
pancreatic cancers. Rising serum levels of CEA may indicate
disease recurrence many months prior to clinical manifestations.
Cancer antigen 125 (CA-125) is a glycoprotein associated
with ovarian carcinoma cells. Elevated levels appear in about
75 per cent of ovarian cancer patients and may be associated
with tumor burden and recurrence. CA-125 is used to monitor
patients for residual or recurrent disease.
Alpha-fetoprotein (AFP) is an oncofetal antigen that is useful
in monitoring patients with nonseminomatous testicular cancer
and certain types of ovarian cancer. Human chorionic gonadotropin
(hCG) is a hormone that can be detected to assess the prognosis
and to monitor treatment response in patients with germ cell
tumors, breast cancer, choriocarcinoma, and testicular carcinoma.
Flow
cytometry has recently become an important clinical
test to determine cellular DNA ploidy (the number of sets
of chromosomes in a cell) and S-phase (the percentage of cells
in active DNA synthesis). In flow cytometry, cells are stained
with a special dye and then analyzed in a flow cytometer by
using a laser beam to measure the fluorescence of cells. The
results are charted in a histogram showing the distribution
of DNA in the cells. Results of flow cytometry are helpful
to determine prognosis, monitor treatment response, and document
tumor recurrence. Tumors demonstrating an abnormal number
of chromosomes, such as tetraploidy, polyploidy, or aneuploidy,
are more likely to be aggressive than tumors that are diploid
(that have the normal two sets of chromosomes). Tumors with
a low S-phase have a better prognosis.
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