Eva wrote:
>
> ---------------
> I looked up Xeloda, and except for being a pill rather than an IV, it sounds
> like a standard chemo drug rather than a "targeted" treatment. I'm going by
> the side effects that are listed--hair loss, hand & foot syndrome, mouth
> sores, constipation--which are like what I had on Adriamycin & Cytoxin, my
> first chemo. These were pretty awful. Why does Tykerb have to be taken with
> Xeloda, specifically?
>
>
OK, I'll give it a go.
Xeloda is basically the same as the long established chemotherapy drug
5FU, but in a form which can be taken orally and gets converted to 5FU
in the body. So it is indeed a 'standard' chemo drug. It known to be
is effective alone or in combination with
Taxotere for metastatic patients.
This class of drugs interferes with the cell division mechanism,
corrupting the copying of DNA among other effects. As with most
chemotherapies it has significant and dose-limiting side effects.
Tykerb is a growth factor blocker that attacks both the receptor
attacked by
Herceptin (HER2) and another one (EGFR). In this it acts on
those receptors in the same way that
Tamoxifen acts on estrogen receptors
The primary reason why it is prescribed in combination with Xeloda is
that it works. Tykerb is a new drug, and not all possible combinations
have been tested. It is known that it produces a major improvement over
Xeloda alone in a certain class of patients, and that the two drugs do
not interfere with each other.
That begs the question why test that particular combination. One reason
is that receptor blockers (including hormone therapy) slow or stop the
growth of tumours but do not actively destroy them. In the adjuvant
setting, where there is believed to be no sizeable tumour present, it is
up to the immune system to destroy any cancer cells that appear. But we
are talking about metastatic disease, where simply halting growth is not
enough, we need to be actively demolishing the tumours as well, to
reduce symptoms. Hence it is logical to combine these agents with
chemotherapy, and the combination is indeed proven to be effective.
One reason to chose Xeloda as the chemotherapy agent is that both drugs
can be administered orally, simplifying the procedure. Another is that
the patients eligible for this drug under the current approval will
already have recently had a taxane, an anthracycline and Herceptin, so
the choice of agents available is restricted, and 5FU is an obvious choice.
Tim Jackson
Xeloda question (reposted) 
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