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Breast Cancer and Tamoxifen





Therapy for

breast cancer

may trigger

even worse


August 26th, 2009

The Belefast Telegraph


Long-term use of

one of the most common

treatments for breast cancer

dramatically increases the

risk of developing a deadly

secondary tumour,

a study has shown.

Tamoxifen is the

“gold standard” hormonal

therapy given to thousands

of British women to

improve their chances of

surviving breast cancer.

The drug prevents tumours

being fuelled by the sex

hormone oestrogen.

In women with hormone-sensitive

cancers — who make up the

majority of breast cancer

patients —

it can stop tumours

returning after surgery.




But the new US research

shows that using tamoxifen

also raises the risk of developing

more aggressive and

difficult-to-treat new tumours

that are not dependent

on oestrogen.

The study found five or more

years of treatment with the

drug quadrupled the chances

of an aggressive non-hormone

sensitive tumour appearing

opposite the initial site of

the disease.

“This is of concern given the

poorer prognosis of ER negative

(oestrogen receptor negative)

tumours which are also more

difficult to treat,”

study leader Dr Christopher Li,

from the Fred Hutchinson

Cancer Research Centre

In Seattle, said.




Dr Li’s team assessed the

history of tamoxifen use among

more than 1,000 women from

the Seattle region who were

diagnosed with hormone-sensitive

breast cancer between the ages

of 40 and 79.

The patients included 367

women diagnosed with both

primary hormone-sensitive

cancer and a second tumour

and 728 who only had

a first tumour.




Nearly all the women who

underwent additional, or

“adjuvant”, therapy after

surgery were given tamoxifen.

Comparing patients who

received tamoxifen and those

who did not showed that the

drug reduced the chances of

oestrogen-positive breast

cancer returning by 60%.


it also appeared to increase

the risk of an oestrogen-negative

second tumour developing

by 440%.

The association was not

seen for women who took

tamoxifen for less than

five years.

The scientists,

whose findings are reported

in the journal Cancer Research,

said it was important to weigh

up the risks and benefits

of tamoxifen.




They said the research did

not suggest that women being

treated with the drug should

stop taking it.

“It is clear that

oestrogen-blocking drugs

like tamoxifen have important

clinical benefits and have

led to major improvements

in breast cancer survival rates,”

Dr Li said.


these therapies have risks and

an increased risk of ER negative

second cancer may be one

of them.


the benefits of this therapy

are well established and doctors

should continue to recommend

hormonal therapy for breast

cancer patients who

can benefit from it.”






3 Responses to “Breast Cancer and Tamoxifen”

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