Women who have had early stage breast cancer surgically removed, and whose tumour cells are stimulated by the hormone oestrogen, can benefit from taking Luteinizing hormone releasing hormone (LHRH) antagonists, a Cochrane Systematic Review has concluded. This medication may be taken alone or alongside the use of tamoxifen.
Developing effective treatment regimes is important because approximately 30% of women diagnosed with early stage breast cancer eventually die of the disease.
In over half of the premenopausal women who develop breast cancer, the cells in the tumours grow faster in the presence of oestrogen. Their tumours are said to be ER+. Treatment often starts with the surgical removal of the tumour, but some cancer cells may be left behind. The challenge then is to slow down their rate of growth.
A well recognised chain of events leads to oestrogen-stimulated tumour cell growth. First LHRH causes the pituitary gland to release luteinizing hormone (LH). This LH travels to the ovaries and triggers the release of oestrogen. The oestrogen moves to the region of the tumour where it locks on to receptors on the cells and stimulates tumour growth.
There are two possible ways of preventing oestrogen from stimulating growth. One is to block the oestrogen receptors that are present on the cells so that they can't respond to the hormone. Tamoxifen works this way. The second is to reduce the amount of oestrogen that is present in the bloodstream. This can be done by blocking LHRH's ability to cause a release of LH.
A team of Cochrane Researchers searched for evidence on the value of using LHRH antagonists. They identified 14 randomised trials that involved nearly 12,000 premenopausal women with operable breast cancer, most of whom were ER+. The LHRH agonist in most trials was goserelin.
"While we cannot yet recommend using ovarian suppression as the standard therapy for these women, it is possible that LHRH antagonists may reduce the risk of cancer reoccurring and extend survival times in premenopausal women who have early breast cancer that is not known to be ER negative. Given this potential, we eagerly await the results of current clinical trials that could answer this important issue," says lead researcher Rohini Sharma, who works in the Department of Medical Oncology, Hammersmith Hospital, London, UK.
The researchers point out that they were able to determine whether tamoxifen or the LHRH antagonist was better if used alone. They did find that women who used LHRH alone had fewer, or less severe, adverse effects than those on tamoxifen.
The researchers also stress the need for studies that investigate long term effects on women given the various different treatment regimes, and the need to wait for the mature results of studies in order to fully answer this important question.