Breast screening of women aged 70 to 74 provides a notable benefit in terms of early detection, according to the authors of a new Australian study.
The finding supports recent moves by some juristications in Australia and overseas to extend screening programs to women older than 70 years.
"The findings are suggesting that it's useful for women who have been participating in screening aged 50 to 69 to continue participating in screening because screening does seem to lead to earlier detection of cancers," says first author Dr Carolyn Nickson, an epidemiologist from the University of Melbourne.
Traditionally, breast screening has been encouraged forwomen aged 50 to 69 with screening available, says Nickson, and the early trials of screening really focussed on women in this age group.
"So there's been an evidence gap around the benefits of screening women who are older," she says.
"It has been a matter of debate about whether the screening age should be extended upwards."
Nickson says until recently, different states in Australia have taken different approaches to screening women aged 70-74.
"Some states stopped reinviting women who come to screening when they turn 70 but some states stopped reinviting them from the age of 75," she says.
Nickson says these different policy approaches provided a "natural experiment" across Australia that enabled her and colleagues to gather evidence on the benefits or otherwise of screening women aged 70 to 74.
In a study published recently in the journal Breast Cancer Research and Treatment, they report on analysis of records of over 300,000 women across Australia between 1996 and 2005.
They found that, as expected, states that reinvited women aged 70 to 74, to be screened had higher participation rates.
Unlike in younger age groups, however, this greater participation did not increase the overall number of cancers diagnosed.
Nickson says this is probably because most of the women involved in screening would have already had any cancers picked up by screening in earlier years.
The researchers did, however, find that greater screening reduced the size of the cancers detected.
For every 10 per cent more women screened, there was an 8 per cent drop in large cancers - those greater than 15 millimetres in size. This suggested screening was picking up cancers earlier, says Nickson.
There was also some evidence of reduced nodal involvement at diagnosis, but the researchers were not as confident of this finding.
The researchers only looked at invasive cancers and excluded DCIS from their study.
Nickson says the findings support recent moves in Australia to encourage all women aged 70 to 74, no matter what state they are in, to have screening.
This approach has been taken by countries including France, Japan, Korea, the Netherlands and Sweden, she says.