A new review of the use of radiotherapy for breast cancer, involving 20,000 women, has turned up some worrying findings.

On the surface of things, the researchers noted that local recurrence of breast cancer could be reduced by as much as two thirds in those who opt for radiotherapy. This effect was true regardless of the type of patient or the type of radiotherapy used.

Overall survival was somewhat less impressive with an overall 20 year survival rate in women opting for radiotherapy of 37.1 per cent compared with 35.9 per cent of those who did not have the treatment.

But what was more disturbing was that, while deaths directly related to cancer did decline, deaths from other causes increased in those women receiving radiotherapy.

Radiotherapy made little difference to the mortality rates in the first two years of therapy. But looking more closely at the figures, researchers noted that, after year 2, annual mortality rates from breast cancer decreased by 13.2 per cent while deaths from other causes, particularly vascular problems, increased by 21.2 per cent.

The results of this study highlight the problem with short term studies which look only at five year survival rates. Here, the hazards of radiotherapy appeared to grow larger the longer the women were followed up (Lancet, 2000; 355: 1757-70).