Many of the side effects of tamoxifen may be worth risking if you have cancer. However the risk/benefit equation changes considerably if you are healthy and offered the drug as a just in case measure.
Last autumn, the UK and US embarked upon a major study, giving tamoxifen to healthy women supposedly at risk of developing breast cancer to see if the disease could be prevented. The US National Cancer Institute, which began its Breast Cancer Prevention Trial (BCPT) at more than 270 sites across the USA and Canada, has enrolled some 16,000 women aged 35 or older thought to be at increased risk of breast cancer. Half these women will be given the drug for at least five years.Risk is being judged on the number of first degree relatives with breast cancer, whether a woman has children, her age at her first delivery, the number of times a woman has had breast lumps biopsied and her age at the start of her periods. Although many doctors spearheading the programme acknowledge the risks, most justify giving a toxic drug to healthy women on the grounds that the magnitude of the problem of breast cancer and our need to do something about it justifies the risk to individual women.
In his various articles in the medical literature, Dr Samuel Epstein (see p 3) says the fact that tamoxifen may have prevented the reappearance of tumours in women who have had breast cancer may have no bearing on women who haven't yet developed the disease. Also, the drug's success has been demonstrated only in postmenopausal women. Many thousands of fertile women will be given the drug in the trial.
As doctors scramble on to the tamoxifen bandwagon (and hand out the drug to many of their healthy patients even before the results of the trial are known) we can probably expect to see a host of new kinds of cancers exchanged for old ones.