DALLASA new blood test technique to detect breast cancer cells
may be 10- to 100-fold more sensitive than any current techniques,
Jonathan W. Uhr, MD, of the University of Texas Southwestern Medical
Center, Dallas, said at the Susan G. Komen Foundations National
Early diagnosis of breast cancer markedly increases the
proportion of patients who will be cured, Dr. Uhr said.
However, some small cancers detected by mammography may already
have metastasized. It is, therefore, of critical importance to
develop tests that will diagnose the disease at the earliest stage possible.
To that end, Dr. Uhr and his colleagues have developed a test for
detecting breast cancer cells that are shed in the blood from very
small tumors. These cells probably die in the circulation when
the tumor is at an early stage and do not go on to metastatic
growth, he said. However, they can be used to detect
Using the assay, the researchers have found blood tumor cells in 15
of 16 patients with early-stage breast cancer.
The test is based on the principle that breast carcinoma is of
epithelial origin while the blood elements are not. Hence, antibodies
against molecules on the blood elements and antibody against
molecules on epithelial cells can distinguish the carcinoma cells
from the normal blood elements, Dr. Uhr said.
The test is done by coating submicro-scopic iron particles with an
antibody to an epithelial cell surface molecule and using very strong
magnets to purify the rare epithelial cells 10,000-fold
(see Figure). The enriched mixture
is passed through a machine that uses a laser light beam to further
distinguish red cells, white cells, and epithelial cells using
antibodies to each and different dyes that fluoresce differently as
they pass through the laser light beam. This technique can
detect a single epithelial cell in a tablespoonful of blood,
Dr. Uhr said.
The technique is expected to be useful in breast cancer detection at
a very early stage and may also help determine which patients with
early tumors need chemotherapy, whether surgery has completely
removed the tumor, and whether tumor cells that persist in the blood
represent growing metastases or a population of dying or nondividing
tumor cells that may never cause a clinical recurrence.
We are performing tests to give us a genetic
signature for the tumor cells so we can observe the
genetic changes as the tumor evolves and make use of this information
for genetic therapy in the future, Dr. Uhr said.