In 1994, Ibaraki prefecture of Japan introduced a biennial breast cancer screening by mammography for women aged 40 years or over. In 2001, the prefecture extended its screening program by adding annual ultrasound examinations for women aged 56 years or less. This report presents selected statistics from the Ibaraki Breast Cancer Screening Program to evaluate the utility of breast ultrasound in comparison with mammography. The data were from screenings carried out from 2001until 2006.
Of the participants, 91,153 underwent mammography and 72,223 underwent breast ultrasound examination. In a breakdown by age segment, the following numbers of women underwent the screenings. Mammography: 10,106 women aged 40 to 44 years, 9,903 women aged 45 to 49 years, 14,482 women aged 50 to 54 years, and 18,874 women aged 55 to 59 years. Ultrasound: 12,455 women aged 40 to 44, 12,580 women aged 45 to 49, 15,145 women aged 50 to 54, and 9,769 women aged 55 to 59.
The abnormal call rates for women between 40 and 59 years in the five-year age segments were 5.0, 5.7, 5.2, and 4.1, respectively, by mammogram, and 4.6, 5.2, 3.5, and 2.8, respectively, by ultrasound. The cancer detection rates were 0.09, 0.22, 0.21, and 0.20, respectively, by mammogram, and 0.12, 0.24, 0.21, and 0.19, respectively, by ultrasound. The PPV of the ultrasound was superior to that of the mammography in each age segment. Ultrasound was significantly effective in detecting breast cancer in the cancer screening program for woman aged 40 to 49 years.