“The aim of our study was to retrospectively review the performance of FFDM in a population-based screening program and compare it to the gold standard of SFM with respect to recall rate and cancer detection rate,” said Niamh Hambly, MD, from the department of radiology at Mater Misericordiae University Hospital in Dublin, Ireland, who discussed the results at IWDM.
The study examined 163,031 women who underwent breast cancer screening in Ireland between Jan. 1, 2005 and Sept. 30, 2007. Of the cohort, 26,593 (16.3 percent) had FFDM performed on a Sectra MDM, Hologic Lorad Selenia, or a GE Healthcare Essential digital mammography system. The remaining patients (136,438, 83.7 percent) had images acquired via a GE 800T or a Siemens Medical Solutions Mammomat 3000 SFM system.
Images from the national screening program were review by six dedicated breast radiologists using standard mammography alternators for the SFM exams and via a Sectra PACS ID55 mammography review workstation for the FFDM studies. Two radiologists independently read each mammogram and assigned a Breast Image and Data Reporting System (BIRADS) category of 1-5 for each image. All solid masses, category 3-5 microcalcifications and other suspicious lesions were biopsied, according to Hambly.
“All samples were evaluated by a dedicated breast pathologist and all biopsied cases were discussed at a multidisciplinary meeting within a week,” she noted.
Recall and cancer detection rates were calculated for FFDM and SFM. Recall was defined as the percentage of women screened who were recalled for further diagnostic workup. The cancer detection rate was defined as the number of cancers detected per 1,000 women screened.
The researchers reported 5,458 women were recalled for further diagnostic work, for an overall recall rate of 3.35 percent. For the SFM cohort, the recall rate was 3.23 percent (4,408 of 136,438) and for the FFDM group, the recall rate was 3.95 percent (1,050 of 26,593).
The overall cancer detection rate was 5.6 per 1,000 women screened. Hambly stated that the cancer detection rate was higher in the FFDM cohort, 6.24 per 1,000 women screened, than in the SFM group, 5.48 per 1,000 women screened.
“This study represents one of the first reviews into the widespread use of digital mammography in a population-based breast screening program,” she said. “The results are very favorable showing a cancer detection rate that is higher than for screen-film mammography. The benefit was apparent in both initial and subsequent screening groups.”