Women with early stage breast cancer revealed by screening are likely to live as long as someone who has never had the disease, figures show.
The NHS Cancer Screening Programme audit confirms detection of the disease in its early stages is vital.
Overall, six out of ten women diagnosed after screening and treated had the same survival rates as the general population.
Experts urged women not to miss screening appointments.
Women with early breast cancer found through screening can live as long as those never affected by the disease
Breakthrough Breast Cancer spokesman
The audit results give an overall picture of the success of the strategy of screening and treatment, rather than a guarantee of cure in every case, as the disease will still come back in a small number of women detected early.
In all, 61% of cancers detected following a mammogram are given an "excellent" or "good" prognosis by doctors based on the size of the tumour and how far it has spread.
After treatment, these patients on average are predicted to have the same lifespan as women who have never had cancer.
However, two out of three breast cancers are not detected by screening, and these are not covered by the audit results.
One woman's battle with breast cancer
Professor Julietta Patnick, who runs the NHS Breast Screening Programme, said that the extension of the scheme by 2012 to cover more women would increase the number found early.
"Huge strides have been made over the past two decades, and more women than ever before are surviving breast cancer, many of whom have benefited from early detection."
Mr Martin Lee, the President of the Association of Breast Surgery, who also helped draw up the report, said it was "vital" that women were aware of the survival rates for breast cancers detected early.
"I would encourage all women who are invited to be screened to attend," he said.
The report also looked at long-term survival for women with more aggressive cancers already past the early stages of development - those not given an "excellent" or "good" prognosis after being detected during screening.
Fifteen years after diagnosis, 86% of these women were still alive, and specialists say that survival is likely to have improved even further since then.
Dr Alexis Willett from Breakthrough Breast Cancer said: "It's excellent news that women with early breast cancer found through screening can live as long as those never affected by the disease.
"As more women become eligible to attend, breast screening services will face increased demand.
"Sufficient resources must be put in place to meet this challenge so even more women can benefit from this life saving service."
A spokesman for Cancer Research UK said: "Results like this demonstrate just how much breast screening matters.
"We've known for some time that the breast screening programme has been saving thousands of lives, but to hear that it's having such a long-term impact is exceptionally good news."
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