The use of computer-aided detection (CAD) was able to improve breast cancer detection in a large prospective trial in the U.K., but double reading without CAD was even better, according to research published in the November issue of Radiology.
"CAD increases sensitivity of single reading by 1.3%, whereas double reading increases sensitivity by 8.2%," according to researchers from St. George's Hospital and the Royal Free and University College Medical School in London.
To prospectively evaluate the recall and breast cancer detection rates with and without CAD in the U.K. National Health Service Breast Screening Programme, a team of U.K. researchers obtained mammograms of 6,111 women (mean age 58.4 years) who were undergoing routine screening between March 21, 2003, and January 9, 2004, at the South West London Breast Screening Service (Radiology November 2005, Vol. 237:1, pp. 444-449).
The mammograms were digitized and analyzed using version 5.0 of Image Checker software (R2 Technology, Sunnyvale, CA). Mammograms were loaded in batches on a roller viewer and accompanied, when available, by previously obtained round screening mammograms.
Twelve film readers participated in the study, seven of whom were consultant radiologists. Five readers were radiographers trained in reading screening mammograms. All mammograms were independently double-read by at least one consulting radiologist.
For each patient, each reader viewed current and available prior mammograms, and recorded an opinion about any visible abnormalities and whether to recall the patient for further assessment. CAD prompts for the current mammograms were then displayed on an adjacent liquid crystal display (LCD) screen, and the reader then reassessed the prompted areas before recording a revised assessment. Recall to assessment was decided after arbitration.
The researchers then determined sensitivities for single reading, single reading with CAD, and double reading, calculated as a proportion of the total numbers of cancers detected by using double readers with CAD.
A total of 62 cancers were found in 61 women, for a cancer detection rate of 1%. Single reading yielded a sensitivity of 90.2%, while single reading with CAD produced a sensitivity of 91.5%. Double reading had a sensitivity of 98.4%.
The recall to assessment rate was 6.1%, with an increase of 5.8% due to CAD. In other findings, it took an average of 25 seconds per reader to read a case without CAD and 45 seconds with CAD.
The CAD software prompted 51 of 61 cancer cases (84%), but readers ignored or overruled 78% of correct prompts on missed cancers.
"With a false prompt rate of 1.59 per case for 6,050 healthy women and a sensitivity of 84% for 62 cancers, readers will have to dismiss 180 false prompts for every true prompt," the authors wrote. "This low specificity may be the major factor explaining why readers are more likely to ignore correct prompts than respond to them."
The study team acknowledged some potential shortcomings with their study, including the lack of confirmation of patient outcome for negative patient mammograms. The researchers also cautioned that the study was not a straightforward comparison of single reading with CAD against double reading, since an extra step of arbitration applied to all women in whom recall was considered, the authors noted.
Single reading with CAD is significantly slower than single reading without CAD, according to the authors.
"Our estimates suggest that use of single reading with CAD as an alternative to double reading would increase the time required," the authors wrote.
By Erik L. Ridley
AuntMinnie.com staff writer
October 25, 2005
Related Reading
Sharp rise in U.K. breast cancer survival rates, October 10, 2005
Breast cancer drug move gives hope to U.K. patients, October 6, 2005
Jury is still out on U.K. CAD utilization, October 5, 2005
Computer-aided detection system helps diagnose breast cancer, September 6, 2005
Despite flaws, lung CAD earns second-reader role, September 5, 2005
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