SECOND OPINION: HEALTH

PART of the current treatment for breast cancer is chemotherapy with drugs that kill cancer cells. The theory is straightforward: the surgeon removes the tumour, but some small cancer cells may have spread in the blood and lymph systems to other parts of the body. Anti-cancer drugs given shortly after the surgery are intended to kill these symptomless but potentially lethal cancer nests. This chemotherapy has unpleasant side effects and many women may wonder just how much it improves their chances of cure.

The New England Journal of Medicine (vol 332, pp 901-11) published the results of 20 years' observation of women with breast cancer treated in a controlled trial in Italy. It began in Milan in 1973 and involved 386 women aged on average around 51 who had just had a radical mastectomy and in whom the cancer had spread to the lymph nodes removed from under the arm. Treatment with three anti-cancer drugs was given for 12 months to some women, selected randomly.

More of the women given chemotherapy have survived, but the story is a complicated one. Twenty years on, 137 of the 207 women given drugs had died as against 138 of the 179 women who had only had surgery. Put another way, 34 per cent of the women given chemotherapy had survived as against 25 per cent of the others. Further analysis showed that chemotherapy seemed to have been most effective in those women who had not reached their menopause at the time of their operations: 47 per cent of them were still alive 20 years later as compared with only 22 per cent of the post- menopausal women.

Cancer experts disagree about the most likely explanation for this difference. One theory is that the drugs are effective because they stop the ovaries producing oestrogen. The Italian team believes the older women took lower doses of drugs because they were less willing to accept the side effects. The interpretation of the results is made more difficult since drug treatments have improved in the past 20 years and modern treatments are claimed to be beneficial at all ages. Never-theless, this is the longest follow-up of the results of chemotherapy for breast cancer, and it provides reliable information on the gains in survival a woman may look for in exchange for the distress of chemotherapy.

The women in the Milan trial had advanced disease. Women whose cancers are detected early (by mammography, for example) have much better prospects. The same issue of the NEJM reports a study by the US National Cancer Institute of women with small tumours with no evidence of distant spread. Half were treated by mastectomy and removal of the lymph glands; the remainder had the tumour removed but not the breast (lumpectomy) and were given radiotherapy. Ten years later 77 per cent of women who had had a lumpectomy and 75 per cent of those who had had a mastectomy were still alive: in 72 per cent and 69 per cent there was no evidence of recurrence of the cancer. In women with the most favourable small tumours the 10-year survival rate was 81 per cent.

Early detection remains the best hope for reducing mortality from breast cancer. Improved mammography, with screening every two years, should be the way forward.