The NHS breast cancer screening programme saves 1,400 lives a year, a group of experts says.
Breast cancer screening is saving lives, the committee says
The Advisory Committee on Breast Cancer Screening looked at statistics and trials from the programme, which offers women over 50 a scan every three years.
The committee found it cut the death rate by more than a third and reduced the need for a mastectomy as cancers tended to be detected earlier.
But charities warned some ethnic groups were not being reached by the scheme.
The committee's report on the NHS Breast Screening Programme said it had been highly effective. In 2003-4, 1.5m women were screened and over 11,000 cancers detected.
Since the programme was introduced in 1988, there has been a 50% increase in the number of cancers detected, it added.
However, the programme has also attracted criticism - with some cancer doctors claiming many of the apparently invasive tumours picked up by screening end up being safe, causing unnecessary alarm and in some cases surgery.
Committee chair Professor Valerie Beral, who is also director of Cancer Research UK's epidemiology unit, said screening "saves lives".
"By detecting breast cancer earlier it also provides many women with improved outcomes, reducing the likelihood that they will need to undergo invasive treatments such as mastectomies.
"The available evidence undoubtedly demonstrates that the benefits of the programme greatly outweigh any risks."
Julietta Patnick, director of the NHS programme, said: "I am delighted that these findings recognise the huge contribution the programme is making to women's lives.
"Breast screening is effective in combating this very common disease."
Dr Lesley Walker, Cancer Research UK's director of cancer information, said: "This report has clearly proved its value as a crucial lifeline for women aged 50-70 and will encourage them to attend screening.
"Since breast cancer accounts for one in three cancers of women in the UK, and the risk increases with age, it is important that women over 70 should continue to be regularly screened by asking their GP for an appointment."
Liz Carroll, head of clinical services at Breast Cancer Care, agreed the findings confirmed the benefits of screening.
But she added: "It should be remembered that the importance of attending screening appointments does not remove the necessity of being breast aware, by knowing what is normal for you and reporting any changes to your GP immediately."
And she said the programme may not be reaching everyone - research has shown that fewer than half of people from ethnic minority groups have attended a screening.