National performance indicators for the breast cancer screening program for the 2015–2016 period
Download the tables of all national indicators for the combined years 2015 and 2016, broken down by rank (xls - pdf).
Download the tables of key indicators broken down by technology type for the combined years 2015 and 2016, by rank (xls - pdf).
The organized breast cancer screening program aims to detect the disease at an early stage so it can be treated as soon as possible, with the goal of reducing breast cancer-specific mortality. To maximize benefits and minimize risks—that is, to be effective—an organized screening program must be of high quality and must be evaluated. Here we present the performance indicators for the organized breast cancer screening program for the 2015–2016 period.
Data from all screenings performed as part of the organized screening program across all departments (a total of 99, with the two departments of Corsica evaluated together) were included to form the 2015–2016 national database.
Since women are invited to undergo mammography-based breast cancer screening every two years, the results are presented over a cumulative two-year period. During this 2015–2016 period, 5,070,666 screenings were performed. It should be noted that the overall results summarized here mask significant geographic disparities, as can be seen by examining the results by department.
The figures provide information on the number of women screened, screening results, and diagnostic evaluations for the 2015–2016 period, as well as the corresponding rates and percentages.
For the 2015–2016 period, 4% of screenings were first organized screenings with no prior mammography history (hereinafter referred to as “true initial screening”), 14% were first organized screenings with a history of mammography (most often as part of an “individual” screening), and 82% were subsequent organized screenings.
Positive Screenings
The rate of positive mammograms (i.e., those judged abnormal or suspicious) on first reading (L1) prior to further evaluation is 13.7 per 100 women undergoing a "true" initial screening. For women undergoing a subsequent screening, this rate is 6.4%. An immediate diagnostic evaluation (BDI) is then performed (96.9% of cases).
The rate of positive mammograms on second reading (R2) is 1.7 per 100 women undergoing a "true" initial screening and 1.0 per 100 women undergoing a follow-up screening. A deferred diagnostic evaluation (DDE) is performed in 81.7% of cases.
Ultimately, the rate of positive mammograms on first or second reading before evaluation (equivalent to the “European recall rate”) is 15.2 per 100 women undergoing a “true” initial screening and 7.4 per 100 women undergoing a subsequent screening. The rate of positive screenings after diagnostic workup is 8.3% for “true” initial screenings and 3.0% for subsequent screenings.
Overall, these results are stable compared to the 2013–2014 period. However, there has been a slight decrease in positive mammograms on second reading, linked to improved performance in the initial readings.
Detected Cancers
The figures provide information on the number of cancers detected and their characteristics for the 2015–2016 period. Indicators TC01 and PC02 through PC10 present the corresponding rates and percentages.
At the time of data extraction, 38,905 cancers (invasive cancers and ductal carcinomas in situ) had been recorded for the 2015–2016 period, representing an overall rate of 7.5 cancers per 1,000 women screened. This rate is 20.6 per 1,000 women undergoing an "initial" screening and 6.9 per 1,000 women undergoing a follow-up screening. These rates are similar to those for the 2013–2014 period.
The percentages of cancers with a favorable prognosis among all detected cancers are important indicators for evaluating the program’s performance:
Among women undergoing a "true" initial screening, 11.7% of cancers with known invasive/in situ status were in situ cancers, 24.2% of cancers with known size were 10 mm or smaller, and 64% of cancers with known lymph node status had no lymph node involvement. These figures show a slight increase compared to 2013–2014.
Among women undergoing follow-up screening, 14.2% of cancers with known invasive/in situ status were in situ cancers, 37.6% of cancers with known size were 10 mm or smaller, and 78.0% of cancers with known lymph node status had no lymph node involvement. These figures show a slight decrease compared to 2013–2014.
Finally, for every 100 cancers detected in 2015–2016, 2.8 were detected through the second reading among women undergoing a “true” initial screening and 5.9 among women undergoing a follow-up screening. The latter percentage is slightly lower than in the 2013–2014 period.
Positive Predictive Value of Screening
The following indicators represent the positive predictive values (PPV) prior to diagnostic evaluation. Calculating positive predictive values for screening within the program requires knowledge of the outcome of the screening procedure. At the time of data transmission to Santé publique France, this information is not always final. At the close of the 2015–2016 database, the information was final for 98.8% of screened women and for 92.8% of women who had positive screening results prior to diagnostic evaluation.
The positive predictive value (PPV) of screening mammography prior to diagnostic evaluation (indicator VPP01 in the screening indicators guide)—that is, the probability of having cancer if the screening mammogram is positive on the first or second reading, prior to diagnostic evaluation (immediate or delayed)—is 9.4%. It has been steadily increasing since the widespread adoption of screening.
Digital Mammography
Since 2008, digital mammography has been authorized in the national program in addition to analog technology. Two main types of digital technologies are used: full-field (digital radiography, DR) and fluorescent plates (computer radiography, CR). Over the 2015–2016 period, only 3.7% of screenings were still performed using analog technology. Among digital technologies, 26% were performed using “CR” digital technology and 74% using “DR” digital technology. The share of DR technology has increased further compared to the 2013–2014 period. The rate of technically correct images is nearly 100% for all three technologies.
The crude positivity rates on first reading prior to further evaluation, as well as the rates of detected cancers, are higher for digital than for analog. And among digital technologies, these rates are higher for DR than for CR. Consequently, the contribution of the second reader appears to be lower with digital DR technology, since the rate of positive mammograms on second reading prior to further evaluation and the percentage of cancers detected by the second reader among all detected cancers are lower. These results hold true regardless of the screening stage
If we focus solely on subsequent rounds—that is, 82% of screenings from the 2015–2016 period—we observe that the percentages of cancers with a good prognosis are higher with digital technology, and particularly with digital DR. These better results for DR are also observed for "true" initial screenings, except for the percentage of in situ cancer. The PPV of positive screenings prior to further evaluation is also higher.
It should be noted that the differences observed between the three types of mammography do not correspond solely to differences in technological performance: confounding factors, notably the experience of radiologists, also play a role.
