Giving breast cancer patients fewer but larger doses of radiotherapy may be as safe and effective as smaller, more frequent doses, according to research published today.

Cancer experts believe the study could have profound effects on the way the condition is treated. At present people who have had cancerous lumps removed from their breasts have 25 small doses of radiotherapy - five a week for five weeks. But giving them 13 larger doses appears to be just as safe and possibly more effective in reducing the risk of relapse, the study published in the Lancet Oncology says.

The trial, carried out by teams from the Royal Marsden hospital, the Gloucestershire Oncology Centre, the Institute of Cancer Research, and the University of Wisconsin in the US, followed 1,410 women who had had a lumpectomy for early breast cancer over 10 years.

The patients were divided into three groups: one was given the standard treatment of 25 doses over five weeks and the other two were given 13 doses in two different, slightly larger, amounts over the same period. The study found that those getting 25 doses had a 12.1% chance of the cancer recurring within 10 years, while the patients given 13 doses had a 9.6% risk on one level of radiation and 14.8% on the slightly lower level.

The researchers, headed by John Yarnold, a professor of clinical oncology at the Royal Marsden NHS foundation trust and Institute of Cancer Research, say the clinical implications could be profound. Professor Yarnold said: "We think it should be possible to give fewer but higher daily doses of radiotherapy to the breast to prevent cancer from returning without harming the patient's healthy tissues. However, we will have to wait for the results of our further trials." Results from a similar study of 4,500 women are expected later this year.

The findings could mean simpler, less disruptive treatment for breast cancer patients - and potential savings for the NHS. A reduction in the number of hospital visits could lessen anxiety for patients and save valuable time and money, said Cancer Research UK, which funded the study.

Lesley Walker, director of cancer information at the charity, said: "If these results are confirmed in the larger follow-up studies it could mean better outcomes with fewer hospital visits for patients."

Maria Leadbeater of Breast Cancer Care said: "Breast cancer patients tell us of the enormous stress and exhaustion they suffer when forced to travel daily for five weeks of radiotherapy treatment. This could mean an end to weeks of ongoing treatment and a tangible improvement to the quality of patients' lives."

Prof Yarnold said the study also suggested even fewer treatments might be possible in the future. "If 13 or 15 treatments are at least as good as 25, what is the limit? Can you go further? We are testing five treatments over five weeks, at the moment, but could you do that over one or two weeks?"