The organized breast cancer screening program aims to detect the disease at an early stage so that 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 2017–2018 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 2017–2018 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 the 2017–2018 period, 5,139,508 screenings were performed. It should be noted that the overall results summarized here mask significant geographical disparities, as can be seen by examining the results by department.

The data presented provide information on the number of women screened, screening results, and diagnostic evaluations for the 2017–2018 period, as well as the corresponding rates and percentages.

For the 2017–2018 period, 4.1% of screenings were first organized screenings with no prior mammography history (hereinafter referred to as “true initial screening”), 12.6% were first organized screenings with a history of mammography (most often as part of an “individual” screening), and 83.3% were subsequent organized screenings.

Positive Screenings

The rate of positive mammograms (i.e., those judged abnormal or suspicious) on first reading (L1) prior to diagnostic evaluation is 14 per 100 women undergoing a "true" initial screening. For women undergoing a subsequent screening, this rate is 6.3%. An immediate diagnostic evaluation (BDI) is then performed (97.3% of cases).

The rate of positive mammograms on second reading (R2) is 1.8 per 100 women undergoing a "true" initial screening and 0.9 per 100 women undergoing a follow-up screening.

Ultimately, the rate of positive mammograms on first or second reading prior to evaluation (equivalent to the “European recall rate”) is 15.5 per 100 women undergoing “true” initial screening and 7.2 per 100 women undergoing follow-up screening. The rate of positive screenings after follow-up evaluations is 8.7% for “true” initial screenings and 3.0% for subsequent screenings.

Overall, these results are stable compared to previous periods. However, there has been a slight decrease in positive mammograms on second reading, attributable to improved performance in the initial readings.

Cancers Detected

The data presented provide information on the number and characteristics of cancers detected during the 2017–2018 period.
At the time of data extraction, 40,120 cancers (invasive cancers and ductal carcinoma in situ) had been recorded for the 2017–2018 period, representing an overall rate of 7.6 cancers per 1,000 women screened. This rate is 20.8 per 1,000 women undergoing an initial "true" screening and 6.9 per 1,000 women undergoing a follow-up screening. These rates are similar to those for the 2015–2016 period (20.6‰ and 6.9‰, respectively).

The percentages of cancers with a favorable prognosis (in situ, size ≤10 mm, no lymph node involvement) among all detected cancers are key indicators for evaluating the program’s performance:

• Among women undergoing a "true" initial screening, 10.4% of cancers with known invasive/in situ status were in situ cancers, 21.8% of cancers with known size were 10 mm or smaller, and 63.4% of cancers with known lymph node status had no lymph node involvement. These figures are slightly lower than those for the 2015–2016 period and fall slightly short of desirable European benchmarks (between 10% and 20% for in situ cancers, ≥25% for cancers ≤10 mm in size, and ≥70% for cancers without lymph node involvement).

• Among women undergoing follow-up screening, 13.8% of cancers with known invasive/in situ status were in situ cancers, 37.0% of cancers with known size were 10 mm or smaller, and 78.9% of cancers with known lymph node status had no lymph node involvement. These figures are stable compared to the 2015–2016 period and in line with desirable European benchmarks (between 10% and 20% for in situ cancers, ≥ 30% for cancers ≤ 10 mm in size, and > 75% for cancers without lymph node involvement).

Finally, for every 100 cancers detected in 2017–2018, 3 were detected through a second reading among women undergoing a “true” initial screening and 5.3 among women undergoing a follow-up screening. These percentages are stable compared to the 2015–2016 period.

Positive predictive value of screening

Calculating positive predictive values for screening within the program requires knowing 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 2017–2018 database, the information was final for 98.8% of screened women and for 93.5% of women who had positive screening results prior to diagnostic evaluation.
The PPV of screening mammography prior to diagnostic evaluation—that is, the probability of having cancer if the screening mammogram is positive on the first or second reading (i.e., judged abnormal or suspicious) before diagnostic evaluation (immediate or delayed)—is 9.7%. It has been steadily increasing since the widespread adoption of screening, reflecting a decrease in the number of false positives (mammograms incorrectly classified as positive) and thus an improvement in the quality of mammograms.