Clue Found to Breast Cancer Drug Resistance
LONDON (Reuters) - Scientists have discovered why some breast
cancer patients do not respond to the drug tamoxifen, in a
finding that could improve treatment and save lives from the
disease that afflicts a million women worldwide each year.
Tamoxifen is the most widely prescribed drug for breast cancer
and has been credited with improving survival of women with the
Breast cancer patients with tumors that use estrogen to grow are
routinely given the drug, but it does not work in all women.
Researchers at Cancer Research UK said on Wednesday they have
found a change in a molecule that explains why, and they are
developing a standard test to detect which patients will not
respond to the drug and would benefit from alternative treatments.
"When you give patients tamoxifen the only way of measuring response
is by seeing whether the tumor continues to grow or not. If you
can determine how the patient will respond you could put them
on tamoxifen or a more appropriate treatment. So it (the finding)
will likely save lives," said Dr. Simak Ali of Imperial College
Tamoxifen works by neutralizing the action of the hormone oestrogen,
which stimulates breast tumor growth. It blocks the function
of the oestrogen receptor (ER), which around half of breast tumors
rely on for their growth.
Studies have shown that it is effective in treating early and
advanced breast cancer, particularly in women older than 50 who
are most likely to develop the disease. But the drug can also
increase the risk of a rare form of cancer of the uterus.
After studying the ER, Ali and his team noticed that part of the
molecule is altered in some women and instead of being blocked
by tamoxifen, it becomes more active. Their research is published
in the journal Oncogene.
"Chemical alteration seems to switch the ER molecule into a completely
different state, in which it becomes immune to the inhibitory
effects of tamoxifen," said Ali.
"It's important that we learn to identify women who are not going
to respond to the drug."
[07/26/2002; Reuters Health]
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