Fewer than 1pc of target group screened for breast cancer
Just 640 of the 100,000 women in the 65-69 age group have been screened for cancer under Breastcheck.
The Government promised a 2014 date in the Programme for Government to bring in the extension to the free scheme, which had been confined to women aged 50-64 but was delayed due to lack of funds.
The Health Service Executive (HSE) confirmed Breastcheck managed to invite just 1,000 women in the older age group in the last quarter of 2015 and give free mammogram X-rays to 640 before the end of the year.
Asked why progress appeared to be slow, a spokeswoman said the age extension is being implemented as planned on an incremental basis, over three screening rounds.
"The additional eligible population is approximately 100,000.
"When fully implemented, over 540,000 women will be included in the Breastcheck programme," she said.
The Irish Cancer Society has estimated that screening women in their mid- to late-sixties will save around 87 lives a year.
One in 10 of all cancers occur in the 65-69 age group. They have the second-highest incidence of breast cancer and the second-highest risk of dying from it.
It is estimated that one life will be saved for every 500 women screened.
The HSE said the benefit of screening is in the repeat nature of the test at defined intervals.
"For mammography screening to be effective, a woman needs to be screened every two years."
The target for this year is to screen 5,500 women in the older age group.
"This is in addition to the 144,000 in the 50-64-year age group," she added.
The most recent Breastcheck report shows 177,724 eligible women were invited for screening, with 135,966 attending. "The uptake rate was 76.5pc, a significant increase from the previous year at 70.2pc.
"During the reporting period 890 women had cancer detected."
She said: "Women of any age who have concerns about breast cancer should seek the advice of their GP, who will if appropriate refer them to the symptomatic breast services in one of the eight designated centres."
Health Minister Leo Varadkar said the age extension is being implemented on an incremental basis "in line with the capacity of the system to manage the additional screening and follow -up workload".
He said that the process will continue, with women being invited for routine screening every two years until they reach the age of 69.
Meanwhile, the Irish Cancer Society announced it is investing €450,000 over the next five years to blood cancer research, which will benefit more patients across Ireland.
Blood cancers make up approximately 10pc of all cancers and include leukaemia, lymphoma and myeloma.
They affect 1,500 people annually.