Mammograms are used to detect breast tumours
Screening women in their early 70s for breast cancer does save lives, a Dutch study of over 860,000 women suggests.
The research, detailed at the European Breast Cancer Conference in Berlin, showed deaths fell by 30% after the upper age limit was extended.
Even though cancer risk increases with age, experts have been divided over whether the over-70s should be checked.
In the UK, there are plans to raise the upper age limit for routine screening from 70 to 73 by 2012.
The Netherlands extended its programme to cover women up to 75 in 1998.
The researchers from the Erasmus Medical Center in Rotterdam looked at breast cancer deaths from 2003 - estimating that the effect of the screening extension would be seen by then.
They found there was a steady decline in deaths from breast cancer in women aged 75 to 79 - the age group where improvements in survival would be seen.
Between 1986 and 1997 the average was 166 deaths per 100,000 women, while in 2006 it was 117 per 100,000 - a fall of almost 30%.
'Request a check'
Jacques Fracheboud, who led the research, said: "The reduction in breast cancer mortality shows that the screening has started to have a statistically significant effect."
The study also found that more women aged 70 to 74 were sent for further checks after screening, compared with those aged 50 to 69 - and a higher proportion of the older age group were confirmed to have breast cancer.
Mr Fracheboud said: "It is easier to find cancer in older women due to their breast tissue being less dense."
But he added: "There is not necessarily an argument for continuing screening beyond 75 because many tumours found at this stage are slow-growing and may never reach the stage of causing a problem."
A spokeswoman for the NHS Cancer Screening Programmes said: "At present, women are invited for screening seven times at three yearly intervals between 50 and 70 years.
"This will gradually be extended to nine screening rounds between the ages of 47 and 73 by 2012, with a guarantee that women will have their first screening by the age of 50.
"Over 200,000 more women will be screened each year as a result."
She said older women were not currently invited in for checks because there was not conclusive evidence that was beneficial.
But she added: "All women attending their final invited breast screening are encouraged to book another appointment in three years' time, if they wish to."
Liz Carroll, clinical nurse specialist at the charity Breast Cancer Care, welcomed the raising of the upper age limit to 73, but said: "Much more must be done now to encourage women in every community to take up invitations to regular screenings and to request screening after 70."
Dr Alexis Willett, of Breakthrough Breast Cancer said: "The risk of developing breast cancer increases with age, which is why we encourage all women over 50 to attend NHS breast screening appointments when invited and for women over 70 to request their own appointment via their GP."