There
is a a new biologic approach for the treatment of breast cancer
that attacks breast cancer at its genetic origins. This new
medicine, Herceptin (trastuzumab) is approved for use
alone in certain patients who have tried chemotherapy with little
success or as a first-line treatment for metastatic disease
when used in combination with paclitaxel (Taxol).
For
certain women with advanced disease, this drug can mean new
hope. There are about 1.6 million women have been diagnosed
with breast cancer in the United States with 180,000 new cases
diagnosed each year and about 50,000 women could benefit from
this drug.
Herceptin,
is a monoclonal antibody bioengineered from part of a mouse
antibody which is altered to closely resemble a human antibody.
On the surface of cells there are receptors that regulate certain
cell functions.
A
change in, or excess of the receptors can cause a cell to change
it's character, for example becoming cancerous. Herceptin binds
to a protein called HER2 which is found in excess on the surface
of some breast cancer cells. Both, men and women, carry the
HER-2 gene. But, the HER-2 excess develops only in malignant
cells and not in normal cells. No one has figured out how or
why this occurs.
After
binding to the cancer cells, Herceptin than kills the cancer
cells, leaving healthy cells behind. About 30 percent of women
with breast cancer have an excess of this protein HER2, which
makes tumors more aggressive. Only patients who have tumors
with this characteristic have been shown to benefit from using
Herceptin.
When
used in breast cancer patients who expressed the HER2 protein,
Herceptin has been shown to slow tumor growth and shrink tumor
size by half. When Herceptin was used alone or together with
chemotherapy drug, there was a dramatic decrease in the number
of tumors, and an increase in the amount of time before the
disease spread to other areas by about three months.
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Chemotherapy
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| The
use of chemical agents in the treatment or control of disease
or mental disorder. |
The
combination of Herceptin together with chemotherapy is more
effective that chemotherapy alone. Herceptin does not cure cancer,
but it does extend the lives of terminal breast cancer patients,
whose cancer returned following chemotherapy. The improvement
was small-about four months on average- but this is especially
noteworthy in a disease that until now has eluded any efforts
to slow its progression to death.
The
women who responded best to Herceptin had the highest levels
of HER2 protein. Testing of tumors from women with metastatic
breast cancer is critical for the identification of patients
who over express HER2 and who can potentially benefit from treatment
with Herceptin. A new test, the DAKO HercepTest, to measure
HER2 protein in tumors and help identify patients who may benefit
from Herceptin is available.
Making
sure to select the patients who are most likely to benefit is
also important because along with the benefit for certain patients
also come possible serious risks. The use of Herceptin either
alone or in combination with chemotherapy can result in a weakening
of the heart muscle which can lead to congestive heart failure.
This
potentially life-threatening side-effect was most common in
patients who received Herceptin in combination with chemotherapy
consisting of anthracyclines and cyclophosphamide (AC). Because
of this serious risk, all patients treated with Herceptin should
have their heart function evaluated before starting treatment
and be closely monitored during treatment.
Women
who have heart problems and their doctors must be extremely
cautious in deciding whether the potential benefit is worth
this risk.
Patients
are given Herceptin intravenously once a week. With the first
dose, Herceptin can cause mild chills, fever, pain, weakness,
nausea, vomiting and headache, these side effects decrease with
each subsequent dose. Herceptin unlike chemotherapy, is not
associated with nausea, vomiting fatigue or hair loss, a real
quality of life improvement over other cancer fighting medicines.
Looking
towards the future
That
Herceptin could be used for other cancers as well is presently
being studied. About 20 percent of women with ovarian cancer,
for example, overexpress the HER-2 gene and Herceptin may prove
effective for women with that disease. Other cancers that could
be potential Herceptin targets include gastric, endometrial,
salivary gland, pancreatic, prostate, colorectal and non-small
cell lung cancer.
Even
though there are a number of new drugs aimed at the genetic
causes of cancer being developed and death rates from breast
cancer are falling, there is still a great deal more that needs
to be done.
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