Shift to Digital Mammography Improves Cancer Detection, but Increases Biopsies

Updates on the national performance benchmarks for digital mammography.

The evolving landscape and development of digital technology has improved breast cancer detection rates for diagnostic mammography, a study published in Radiology found; however, abnormal interpretation rates have increased as a result.

In 2005, the Breast Cancer Surveillance Consortium (BCSC) released a study on diagnostic mammography performance, during which time, film mammography was still the standard. With digital technology now replacing film, the investigators wanted to revisit old benchmarks.

“Our goals in this study were to produce benchmarks that individual radiologists and breast imaging facilities can use to compare with their own practices and to convey trends in how the metrics have changed over the past 10 to 15 years,” said lead author Brian L. Sprague, PhD.

Data from 6 BCSC registries, comprising 418 radiologists and 92 radiology facilities, were included in the study. Mammography indication and assessments were obtained on women undergoing diagnostic digital mammography and linked with cancer diagnoses from state cancer registries. Included in the database were 401,548 examinations conducted on 265,360 individuals from 2007 to 2013.

Based on the data, the investigators found that as cancer detection rates improved, the abnormal interpretation rate increased from 8% in 2005 to 12.6% under the new study.

“While the improvements in cancer detection rates are encouraging, the increased abnormal interpretation rate is somewhat troubling in that we’re trying to keep this rate down,” Dr Sprague said.

The authors noted that an increase in mammographic cancer detection does not necessarily result in a significant rise in abnormal interpretation rate. Dr Sprague gave the example of Europe, who has achieved cancer detection rates similar to those in the United States, and with much lower abnormal interpretation rates.

Europe has increased the utilization of double reading, where at least 2 radiologists interpret the same exam, which may be a factor. Dr Sprague also cited variables such as fear or litigation, which could affect abnormal interpretation rates.

The investigators also observed another concerning trend in which there was a drop in positive predictive value (PPV). The results of the study showed that PPV for a biopsy recommended (PPV2) decreased from 31.5% in 2005 to 27.5%.

The lower PPV2s are a result of the abnormal interpretation rate increasing more than the cancer detection rate. These findings suggest that improving imaging could do more to permit the visualization of additional findings than helping in discriminating benign from malignant findings, according to the authors.

“The results of the study highlight specific areas where quality improvement initiatives should focus,” Dr Sprague concluded. “Overall, there is a lot of good performance out there, but there are definitely areas for improvement in positive predictive value and abnormal interpretation rate.”