Practice makes perfect? High-volume mammo centers offer better screening outcomes

Women looking to maximize their benefits from breast cancer screening would be wise to seek out a facility with high mammography interpretive volume, according to the results of a new study.

Researchers demonstrated that these high-volume facilities are significantly more like to diagnose invasive tumors with good prognoses, meaning they were caught early enough to maximize treatment effectiveness.

Results of the study were published in the Journal of Medical Screening.

“This addresses an important gap in evidence that informs whether facility volume is associated with good screening outcomes for women – such as finding more early invasive tumors rather than advanced, which helps reduce the likelihood of dying from breast cancer or having more intensive treatment,” said first author Tracy Onega, PhD, a principal investigator at the Norris Cotton Cancer Center at Dartmouth-Hitchcock Medical Center in Lebanon, N.H., in a press release.

Onega and colleagues reached their conclusions by examining annual interpretive volumes at 116 facilities participating in the U.S. Breast Cancer Surveillance Consortium. The data covered more than 3 million screening mammograms from 2000 to 2009, and included nearly 10,000 cancers that were screen-detected within one year of the exam.

Of the facilities included in the analysis, 80 percent had annual interpretive volumes of more than 2,000 cases, and 42 percent had volumes greater than 5,000.

Facilities with a total volume of 5,000-10,000 were 32 percent more likely to diagnose invasive tumors with good prognoses compared with facilities that interpreted 1,000-2,000 cases per year.

“Good prognosis” was defined by the authors as screen-detected invasive cancers smaller than 15 mm, at an early stage and lymph node negative at diagnosis.

The authors also noted a concomitant decrease in tumors with poor prognosis, as the high-volume group of facilities was 22 percent less likely to diagnose poor prognosis cancers than the low-volume group of facilities.

In a statement, Onega said facility-level mammography quality monitoring should focus on tumor characteristics. She also noted that the threshold of 2,000 annual interpretations should be easier to handle with digital mammography, as smaller facilities can send cases to be interpreted by larger facilities.

“Studies to isolate the mechanism by which volume affects quality may guide interventions to achieve similar performance gains among smaller volume facilities,” Onega said. “[W]e’ve now laid the foundation to study the volume benchmarks in a more granular way before this could translate directly into policy and practice changes.”