Trends in Mammography Indicate Better Detection of Cancer, More Biopsies
The switch from film to digital technology in mammography use has improved cancer detection, but also has downsides.
The switch from film to digital technology seems to have improved detection of cancer with diagnostic mammography while also increasing the abnormal interpretation rate, which may result in more women undergoing unnecessary biopsies.1
This study used data from the Breast Cancer Surveillance Consortium (BCSC). The BCSC is comprised of many varied breast imaging facilities that link data with state cancer registries to track breast cancer screening and diagnosis in the United States.
The BCSC released results on the performance of diagnostic mammography in 2005. In the United States, women undergo diagnostic mammography when they present with clinical symptoms, following an abnormal screening mammogram, or if undergoing short-interval follow-up for a previous finding analyzed as probably benign.
This study revisited the previous benchmarks. In 2005, film mammography was standard.
"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 study co-investigator Brian L. Sprague, PhD, from the University of Vermont Cancer Center in Burlington.
This study examined data from 6 BCSC registries comprised of 418 radiologists from 92 facilities. Researchers analyzed data from 410,548 examinations in 265,360 women undergoing diagnostic digital mammography between 2007 and 2013. The mammography indications and assessments were linked with cancer diagnoses in state cancer registries.
The cancer detection rate rose from 25.3 per 1000 in 2005 to 34.7 per 1000 between 2007 and 2013. This increase likely reflects improvements in mammography imaging that allow visualization of smaller lesions and better detection of calcifications.
However, the abnormal interpretation rate — the rate at which patients are called back for biopsy — rose from 8% in 2005 to 12.6% between 2007 and 2013.
"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," Sprague explained.
The positive predictive value (PPV), the probability that patients with a positive diagnostic mammogram have a malignancy, in the period from 2007 to 2013 declined from the 2005 PPV rate. .
PPV for a biopsy recommendation (PPV2) decreased from 31.5% in 2005 to 27.5% in 2007 to 2013. These results were due to the fact that the abnormal interpretation rate increased much more than the cancer detection rate.
"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."
1. Lehman CD, Arao RF, Sprague BL, et al. National performance benchmarks for modern screening digital mammography: update from the Breast Cancer Surveillance Consortium . Radiology. 2016 Dec 5. doi: 10.1148/radiol.2016161174 [Epub ahead of print]