What is less well known is that tamoxifen is useless for around 30 per cent of women with breast cancer because they have a form of the cancer that does not respond to oestrogen (Lancet, 1998; 351: 1451-67).

Because it appeared to work in more advanced breast cancers, in the 1990s, tamoxifen began to be used for DCIS - again with initially glowing headline research results. But, as more and more symptomless, essentially healthy women were being given the drug, it soon became clear that the medicine was worse than the disease it was meant to prevent.

Reports came tumbling in that tamoxifen was causing osteoporosis, retinopathy, stroke, blood clots, and cancers of the womb, ovaries, liver and gastrointestinal tract - and some of the cases were fatal (J Gen Intern Med, 2003; 18: 937-47). The most serious side-effect has been endometrial cancer, forcing the World Health Organization to classify tamoxifen - the supposed miracle anticancer drug - as a group 1 carcinogen (cancer-causing agent).

That was in 1996, yet doctors continue to prescribe the drug for DCIS.

Six years later, in May 2002, the Food and Drug Administration (the highly conservative US government healthcare agency) finally issued an official warning against tamoxifen, pointing to the 'serious, life-threatening or fatal events' caused by the drug, and questioning its whole prescribing rationale, including for women 'at high risk of cancer' (FDA statement, 15 May 2002).

Radiotherapy for DCIS Besides tamoxifen, ‘just-in-case’ DCIS treatment also includes radiotherapy, where X-rays are targeted on the cancer area - even though, of course, there is no actual cancer.

In some women, radiotherapy itself can cause cancer, in particular, a rare 'aggressive' cancer called ‘angiosarcoma’; this is almost always fatal (J Am Acad Dermatol, 2003; 49: 532-8).

Lung cancer, too, is a not uncommon effect of breast radiotherapy. Of 31 patients who had received radiotherapy for breast cancer, a staggering 19 went on to develop lung cancer - mostly on the same side as the irradiated breast (Med Oncol, 1994; 11: 121-5). Breast cancer patients also risk having soft-tissue cancer of the breast (Int J Radiat Oncol Biol Phys, 1995; 31: 405-10) and heart damage.

There is no evidence that radiation therapy for DCIS saves lives - 'no trial in patients with DCIS has ever shown a survival benefit with the use of radiation,' says Dr Melvin Silverstein, director of the University of Southern California Breast Center in Los Angeles (Oncology [Huntingt], 2003; 17: 1511-33).

In addition to drug therapy and radiation, conventional treatment for DCIS also includes surgery - either the removal of a small area of tissue or the whole breast. And in the opinion of breast specialist Michael Baum, the very act of piercing the flesh may cause cancer to develop.

Baum points to the theories of Harvard researcher Dr Judah Folkman, who has shown that cancers spread by forming new blood vessels via a process called ‘angiogenesis’.

As angiogenesis also occurs whenever flesh is injured, this may be enough to trigger the cancer process. 'The newly formed blood vessels [after an incision] bring the blood and oxygen that encourage tumour growth,' says Baum. 'They also provide the means for cancer cells to travel to distant organs and form new tumours.'

Baum believes that biopsy can also precipitate cancer. This routine diagnostic technique uses a needle to pierce the skin and cut out a tiny sample of tissue.