Why the limit on breast-cancer drug? And will I have twins, too?

Stopping tamoxifen

Stopping tamoxifen

Q. Five years ago, I developed breast cancer at the age of 57. The cancerous lump was removed and I was treated with chemotherapy and radiotherapy. After these were completed, I started taking tamoxifen. At my annual check-up this month, I was told to stop taking the tamoxifen, because it was no longer necessary. Tamoxifen has kept me well for the past five years, and it makes me feel very uncomfortable to think about stopping it. Is there any logic behind the decision to stop the drug, or is it simply a way of reducing NHS costs?

A. Tamoxifen is a drug that has been used to treat breast cancer for more than 30 years. It works by blocking the effects of the female hormone oestrogen. Some breast cancers seem to be "fuelled" by oestrogen. Tamoxifen blocks this effect. Women who take tamoxifen after having surgery, chemotherapy and radiotherapy are much less likely to suffer a recurrence of their breast cancer. Not all breast cancers are sensitive to oestrogen, and this is why not all women are treated with it. Many women ask why the drug is only given for five years. If it works for five years, why shouldn't it work for 10 or 15 years? The answer is that studies have shown that taking tamoxifen for more than five years doesn't seem to give any additional benefit. Like all drugs, tamoxifen has some unwanted side effects. One of these is that it increases the likelihood of developing cancer of the uterus. So it is important to use it only as long as it appears to help. The advice you have been given is the right advice. If you continue to take tamoxifen for more than five years, you will probably do yourself more harm than good. Even taking tamoxifen for five years is estimated to quadruple your risk of getting cancer of the uterus.

Twin chances

Q. There are quite a few sets of twins in my family, and I would like to know what the chance is that I will have twins. I am a non-identical twin, my mother has a sister and brother who are twins. Two great-uncles were also twins, although no one seems certain if they were identical or non-identical.

A. Non-identical twins do have a tendency to run in families. Identical twins, however, do not seem to be caused by any genetic predisposition. About four in every 1,000 pregnancies result in identical twins. This figure seems to be fairly constant around the world. The likelihood of having non-identical twins varies from country to country. Among white northern Europeans, non-identical twins occur in about six in every 1,000 pregnancies. In parts of Nigeria, up to four in 100 pregnancies result in non-identical twins. Women who have already had one set of non-identical twins are twice as likely to have twins in their next pregnancy, compared with women who have never had twins. For women with a more distant family history of non-identical twins, the likelihood is increased, but it is difficult to give an exact figure. Surprisingly, if a woman's partner has a family history of twins, she doesn't have an increased risk of having twins herself. One theory is that there is a genetic reason why some women release more than one egg at a time. These days, the most common identifiable cause of twins is fertility treatment.

Have your say: readers write

CM tells of his experience of blackheads:

Quinoderm is the only thing that I've found works for blackheads, though it doesn't get rid of them completely. Otherwise, go easy on the Retin-A. It gave me a broken vein in the nose - my fault for putting too much on. I'd rather have the blackhead.

Send questions and suggestions to A Question of Health, 'The Independent', Independent House, 191 Marsh Wall, London E14 9RS; fax: 020-7005 2182; or e-mail: health@independent.co.uk. Dr Kavalier regrets that he is unable to respond personally to questions