| Alternative Cancer Treatments | ||
|
|
|
|
|
|
 |
Understanding HER2
and Herceptin
Those
involved with breast cancer, either professionally, or as a victim, have
usually heard the term “HER” or “herceptin.”
This article defines the terms and
explains the mechanisms involved. HER2
is an acronym for human epidermal growth factor receptor also known as
c-erbB-2/neu. HER2
is classified as a proto-oncogene.
Proto-oncogenes interact with other genes called tumor suppressor
genes in a controlled and regulated way.
When HER2 undergoes mutation, it becomes an oncogene.
HER2 is a gene that contains the blueprint for proteins that act
as receptors on the surface of the cell.
When these receptors are activated by growth factors, a series of
signals are sent from the cell surface to the nucleus via proteins
called tyrosine kinases, starting a cascade of events that leads to cell
division. Many
normal cells have
“copies” of the HER 2 gene, and therefore express small amounts of
HER2 receptors on the cell surface.
In cancer cells, however, a mutation has occurred, and there are
from 10 to 100 times as many HER2 receptors as there should be.
In the world of biochemistry, these is known as overexpression,
or gene amplification. Unfortunately,
overexpression of the HER2 gene usually indicates that the malignancy is
more aggressive, and more resistant to therapies. The HER2 oncogene is
overexpressed in about 25 to 30% of breast cancers and is associated
with a shorter period of disease free survival (DFS) and overall
survival (OS). Recent
breakthroughs in scientific engineering have allowed scientists to
develop monoclonal antibodies that can zero in on particular proteins.
Herceptin (trastuzumab) is the first monoclonal antibody to be
approved by the Food and Drug Administration (FDA) for the treatment of
advanced metastatic breast cancer.
A number of clinical studies have demonstrated significant
improvement in chemotherapy outcomes when Herceptin is added.
Monica
Fornier, M.D. of Memorial Sloan-Kettering Cancer Center in New York
studied 63 patients with metastatic disase.
Patients were treated with Taxol (paclitaxel) and Herceptin.
The response rate (measured as tumor shrinkage of 50% or more)
was 62 percent in patients who overexpressed HER-2 versus 44 percent in
patients who did not. This
is quite significant because usually patients with HER2 positive cancers
respond more poorly. Also,
93% of the patients had been previously treated with chemotherapy which
typically results in more resistant cancers.
Larry
Norton, M.D., also of Sloan Kettering studied 469 women with metastatic breast cancer. He found an increased survival of 25% greater duration when
Herceptin was added (from 20.9months to 25.4months). Another
recent study looked at 469 women who had not had chemotherapy for their
stage 4 cancers. All
patients were HER-2 positive.
One group received Herceptin plus chemotherapy and another
chemotherapy alone. There was significant improvement in time to disease
progression when Herceptin was added.
Women who have breast cancer should ask their oncologists about testing them for HER2, and discuss with them the possibility of using Herceptin in their chemotherapy routine. Article by Michael Guthrie, R.Ph.
|
 |
 |
|
"Alternative Cancer Treatments"
Michael Guthrie,
R.Ph. CGP 2003-2006
|
||
