ADVANCED digital screening is picking up early warning signs which should result in fewer women developing invasive cancer.
BreastCheck, which offers free X-rays to women aged 50-64 years, said the numbers of women diagnosed with cancer that may not be invasive is on the increase.
The detection of this form of cancer, known as ductal carcinoma in situ (DCIS), is on the rise because of the use of advanced digital screening.
It means some of the women diagnosed with breast cancer under the State's free X-ray programme may have received treatment they did not need.
But the annual BreastCheck report says that it was important to spot the warning signs – and that the developments should ultimately result in fewer women developing cancer.
"It is well recognised that low-grade DCIS may not progress to invasive cancer and its detection may lead to a certain amount of overtreatment," said the report.
But it said that most (90pc) of the DCIS cases detected in 2011 were of high or intermediate grade, which do have a greater likelihood of progressing to invasive disease.
"Doctors still cannot tell which case of DCIS will develop into invasive disease and which will not cause danger – so some women inevitably have treatment, such as chemotherapy, they do not need," said the report.
Controversy over breast cancer screening programmes erupted in the UK last year after a review showed a significant number of women diagnosed with the disease will not develop invasive cancer but undergo unnecessary treatment.
But while lead clinical director Dr Ann O'Doherty said she welcomed the findings of the UK review, she also said women needed a diagnosis in order to make an informed choice on how to proceed with treatment.
"The women must be offered clear treatment choices and information after diagnosis in order to help her to make an informed choice on her treatment," she wrote.
She has previously defended the BreastCheck service against accusations that it might lead to "overtreatment" of women.
"There is nothing incorrect about the diagnosis being made. We may be overtreating it but the diagnosis is absolutely correct," she said.
The BreastCheck report said that free mammograms were provided to 125,329 women aged 50-64 during the year, and 832 breast cancers were detected.