ScienceDaily (Sep. 29, 2000) — Stunning advances in the technology of molecular genetics mean that within the next few years, doctors should have the ability to provide a breast cancer patient with her own molecular profile.

That profile will be a unique genetic "fingerprint" that will tell the woman and her doctor how all the genes within her tumour are behaving, which receptors are responding to what stimuli, how much they are responding and precisely which proteins are functioning as co-activators or co-repressors of receptors.

The result will be a complete DNA ‘photofit’ of the tumour that will ultimately be able to determine what treatment, in what amount and for what duration will work best for that woman.

Dr C Kent Osborne, Professor of Medicine and Cell Biology and Director of the Breast Cancer Center at Baylor College of Medicine in Houston, Texas, told delegates at the European Breast Cancer Conference in Brussels today (Wednesday 27 September) that the future was already with us, albeit in a less sophisticated form.

"We already know, for example, which breast tumours are oestrogen-dependent and will respond to hormonal therapies such a anti-oestrogens like tamoxifen. The best marker for response to hormonal treatment is the oestrogen receptor and about a third to a half of all breast cancers are oestrogen-dependent.

"As few as two or three percent of tumour cells expressing oestrogen receptors predict that tamoxifen will be beneficial and tumours that express large amounts will reap even greater benefit with a 50% to 60% annual reduction in recurrence risks if we give tamoxifen adjuvantly."

Dr Osborne said that this knowledge had already led to a significant fall in deaths from breast cancer in some countries where tamoxifen was in widespread use.

"But this is just the beginning. Many centres are working in this field and are already identifying other potentially important markers, such as the progesterone receptors, BcL2 and pS2, which are oestrogen regulated genes - also the HER2 oncogene which tells us that the patient may have less benefit from endocrine therapies.

"We don’t know yet how many genes will turn out to have important predictive value. With up to 100,000 genes in each cell, potentially it could be hundreds or thousands. Obviously the hope is that it will be relatively few – 10 to 15 if we get lucky. But what I am sure of is that within the next five years we will have added enormously to our pool of knowledge about the genetic behaviour of tumours and that will put us on course, not only for producing designer drugs, but for a whole range of treatments tailored to the needs of the individual patient."

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