Background

In 1988, the national Breast Screening Programme (BSP) began offering women aged about 50-64 years triennial mammographic screening (1), and full national coverage was achieved by the mid-1990s (10). In 2000 it was announced that the age range for triennial screening would be extended from 50-64 to 50-70 years. This change began to be implemented in 2004, and was completed within a few years.

Currently, about 80 breast screening units cover all of England, each responsible for a defined area. Each year they invite about 2.8 million women aged about 50- 70, with about 2.0 million accepting (11). The BSP sets standards for the screening units and monitors performance through its national quality assurance network.

In 2007, the Prime Minister announced plans for eventual extension to the range 47-73 years (2), but it was unclear when this would begin. This offered an opportunity to obtain reliable evidence about the effects of extending the age range of triennial screening. Hence, a trial of this age extension has begun, in which only half are offered extra screening, with the effects monitored through routinely collected NHS statistics.

Following a 2009-10 pilot study of the acceptability of cluster-randomisation of additional screening at ages 47-49 and 71-73 in 5 breast screening units (3, 4), the AgeX trial extended recruitment to about five-sixths of the breast screening units in England, and this cluster-randomisation continues.

In 2011, the Government deferred the date when screening would begin to be extended to all women aged 47-73 (5). In 2012, an independent panel set up by the Department of Health and the charity Cancer Research UK reported “The UK breast screening programmes [at ages about 50-70] confer significant benefit and should continue…. The impact of breast screening outside the ages 50-69 years is very uncertain. The Panel supports the principle of the ongoing trial in the UK [AgeX] for randomising women under age 50 and above age 70 to be invited for breast screening” (6).

In 2013, Public Health England (PHE) became responsible for all government screening programmes, and stated that final decisions about extension of the age range would await the emergence of reliable evidence of its effects. In 2015 (in response to a Parliamentary committee report on NHS screening) the Government stated that the AgeX trial would need to continue to invite women for at least two more [triennial] screening rounds [ie, at least 6 more years] (7).Meanwhile, as female life expectancy is increasing, interest has grown in the possible advantages of continuing to screen women not just in their early 70s but throughout their 70s. The advantages and the disadvantages of continuing triennial screening after age 70 would be seen more clearly in a trial of 2 or 3 additional invitations (covering ages 71-76 or 71-79) than in a trial of just one.

Hence, in 2013 the All-Party Parliamentary Group on Breast Cancer in Older Women (APPG) said “Women are not routinely invited for breast screening past the age of 70 … the current 'age extension trial' [of screening past age 70] … should be extended past 73 to 76, and, if appropriate … further extended” (8), and in a separate report in 2015 the APPG reiterated this conclusion (9).

Although AgeX began as a trial of additional screening at ages 47-49 and at ages 71-73, it has therefore become a trial in which the older women allocated additional screening can, if screening resources become available, continue to be invited triennially at ages 71-76 or at ages 71-79, thereby assessing the effects of continuing triennial screening for several years after age 70.