Younger women with a family history of breast cancer should receive annual screenings to pick up the disease earlier, a charity says.
Breast Cancer Now funded a study which found cancers were detected sooner when 35 to 39-year-olds at risk had annual mammograms.
NHS screening often starts at the age of 40 for women with a family history.
Experts need to balance the benefits of doing more checks against causing any undue worry or over-treatment.
The study’s authors said that more analysis was needed on the risks, costs and benefits of extending the screening programme.
But Baroness Delyth Morgan, the charity’s chief executive, called for the government’s forthcoming review of NHS screening programmes in England to consider the introduction of scans for women aged 35 to 39 with a family history of breast cancer.
The study, carried out by researchers at the University of Manchester, offered scans to 2,899 women in this age group who were deemed to have a moderate or high risk of the disease after being referred by a GP to a family history clinic.
The screening detected 35 invasive breast cancer tumours, most of which were small and identified before they had reached the lymph nodes – a sign that they had not spread around the body.
In a control group, which did not have the screening, far fewer of the cancers were discovered when they were still small and more had spread to the lymphatic system.
Prof Gareth Evans, the lead author of the study, said the trial demonstrates that annual scans are effective in detecting tumours earlier for this younger age group.
He said overdiagnosis – where people are treated for cancers that are unlikely to prove harmful – was “far less likely” to be an issue with this younger age group.