The Mammography “Sweet Spot” Recall Rate Is Lower Than Suggested

The appropriate recall rate for screening mammography is lower than currently accepted levels, a new study has found.

The “sweet spot” for optimal cancer detection with both 2D digital mammography and 3D tomosynthesis is 7 percent-to-9 percent – not the 12 percent-to-14 percent that is largely recognized throughout the industry, said a Chicago-based multi-institutional group of researchers.

“The results of this investigation are in contrast to those of a recent study suggesting appropriateness of higher recall rates,” said the group led by Garth H. Rauscher, Ph.D., associate professor of epidemiology at the University of Illinois at Chicago. “Too many women are being called back for diagnostic imaging, and new benchmarks could be set to reduce this burden.”

They published their findings last week in the American Journal of Roentgenology.

With more than 65 percent of women over age 40 undergoing annual screening mammography, identifying the most appropriate recall rate can ensure cancer detection is maximized while unnecessary downstream diagnostic studies and breast biopsies are minimized. But, no consensus exists on what that recall rate should be, the team said.

Recent data from the National Mammography Database has suggested that a 10-percent recall rate is the norm in the United States. An analysis from the U.S. Breast Cancer Surveillance Consortium (BCSC) sets the recall range at 5 percent-to-12 percent. In fact, the team said, nearly half of all radiologists within the BCSC have a recall rate higher than the current 12-percent recall recommendation.

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To identify that optimal recall rate, Rauscher’s team looked at 1,060,655 2D and 3D – 205,817 2D analog exams; 682,352 2D digital examinations; and 172,486 3D digital tomosynthesis exams – from women ages 40 to 79 who were screened between Jan. 1, 2005, and Dec. 31, 2017. Of the group 71 percent of studies had a prior screening mammogram in the data base, and 84 percent of the screening exams in this study were interpreted in the context of those priors.

According to their evaluation, the overall mean recall rate for mammography was 10.7 percent, the cancer detection rate was 4 per 1,000 studies, and the biopsy recommendation rate was 1.6 percent. More specifically, 2D analog exams had the highest recall rate (11.2 percent) followed by 2D digital exams (10.8 percent), and 3D tomosynthesis (9.4 percent). In addition, 3D tomosynthesis had the highest mean biopsy recommendation rate at 1.93 percent. 2D digital exams and 2D analog followed with 1.55 percent and 1.47 percent biopsy recommendation rates, respectively.

There were certain features that were associated with either higher or lower recall rates, as well. Not having a comparison study was linked to a higher rate of recall, biopsy recommendation, and cancer detection. Greater breast density was also associated with a higher recall rate, but it was inversely connected with cancer detection rate. In addition, the team said, lower recall and biopsy recommendation rates were associated with older patient age, as were higher rates detection for both minimally invasive cancer and cancer.

Based on the team’s analysis they determined that recall rates between 7 percent and 9 percent hit that desired sweet spot of maximizing cancer detection and minimizing unnecessary biopsies for both 2D mammography and 3D tomosynthesis. When recall rates climbed above 8 percent, they said, they saw disproportionately increased biopsy rates with little corresponding increase in cancer detection rates.

“This observation is supported by recently published studies, which reported that 3D tomosynthesis was associated with greater specificity and cancer detection rate compared with 2D digital mammography,” the team said. “Thus, with the increased use of 3D tomosynthesis in the United States, the recall sweet spot will likely decrease, as well.”

The team also noted that the radiologists who interpreted the exams in their study did not have a sub-specialty in breast imaging. Consequently, their findings are widely applicable to clinical environments that have few radiologists dedicated specifically to breast imaging.

“Our results should be generalizable to other community-based practices but may not be generalizable to academic and other settings that rely predominantly on breast imaging specialists,” they concluded.

Ultimately, the team said, these findings will contribute to improving the use and efficacy of mammography.

“Too many women are currently being called back for additional diagnostic imaging, and it might be possible through a combination of specialized training, double-reading, or other intervention to reduce the burden of false-positives on patients and the healthcare system without sacrificing early detection of breast cancer,” they said. “In addition, setting a lower benchmark for recall rate could serve to motivate changes that improve the effectiveness of mammography as a cancer screening tool.”