Tomosynthesis Better Long-Term than Digital Mammography for Breast Cancer Screening

Screening women for breast cancer with digital breast tomosynthesis over the long term catches more cancers with fewer false positives than traditional 2D mammography, according to new research.

The findings of a new study published Tuesday in Radiology not only reveal that tomosynthesis outperforms 2D mammography among women in all age groups, but they show the screening tool identifies more aggressive cancers that have poor prognoses, contradicting current thoughts that tomosynthesis only captures less invasive malignancies.

“A test that can change the balance of the risk-benefit to be more advantageous to the woman – to find more cancers while decreasing that false-positive rate – is really good,” lead study author Emily Conant, M.D., professor and chief of breast imaging at the University of Pennsylvania’s Perelman School of Medicine, told Diagnostic Imaging. “We’ve shown that we’re able to do this with tomosynthesis past the first or second round of screening.”

To date, most studies comparing tomosynthesis to 2D mammography have focused on a single round of screening. Instead, this study followed patient outcomes over a five-year period, and in doing so, proved the higher cancer detection rate already attributed to tomosynthesis extends beyond initial screening efforts.

For this study, Conant’s team analyzed more than 56,000 tomosynthesis exams and approximately 10,500 2D mammograms. The participant population was also unique, she said, because African American women – a population known to experience more aggressive breast cancers -- made up approximately 50 percent of the group.

This study’s findings are clinically significant, she said, because not only does the data provide long-term results at the population level, but it also drills down to the individual patient level, offering more refined analysis than previous studies.

The Results & Impact

According to study analysis, tomosynthesis detects more cancers than 2D mammography – 6 cancers per 1,000 and 5.1 cancers to 1,000, respectively. Tomosynthesis also offers a lower screening recall rate over the five-year period. Only 8 percent of tomosynthesis-screened women were made to return for additional scans, but 10.4 percent of women who receive 2D mammograms were called back. This reduction in false positives is significant on a variety of levels, Conant explained.

“False positives are important. They’re anxiety-producing, and they’re frightening,” she said. “They cost not only in emotions, but also in healthcare costs.”

The study results also indicated tomosynthesis does a better job of identifying more invasive, aggressive cancers over the long term. The overall invasive cancer sensitivity for tomosynthesis and 2D mammography were 89.8 percent and 80.4 percent, respectively. Conant largely attributed this improvement in pinpointing more severe cancers to the greater racial and ethnic diversity among the study participants.

“Ours was a very different population from many of the other articles that have been written,” she said. “We know that African American women get biologically aggressive cancers more often at younger ages, and we were able to show that tomosynthesis finds more of those poor prognosis or advanced cancers that 2D screenings.”

Going forward, she said, breast cancer investigators should concentrate more on the biological factors that impact cancer. Doing so can provide further guidance into how best to search for, diagnose, and treat breast cancer in individual women.

“This is important because different cancers really do impact differently. It’s not all about the size of the cancer,” she said. “It has a lot more to do with the receptor type and the biology of the cancer – even the age of the woman. Do we know if she’s pre-menopausal or post-menopausal? The aspect of biology is really important, and that’s where we need to be pushing screening further into the world of biology.”

It’s also important to note, Conant said, that this study revealed the overall false negative rate was lower with tomosynthesis than with 2D mammography.

“We have actually shown that false negatives aren’t that common,” she said. “By having such a large number of cases to show statistical significance, we show a trend down of false negatives with tomosynthesis.”

Still, she reiterated, further research is needed to validate those results.

Overall, according to Samantha Heller, M.D., Ph.D., associate professor and breast imaging fellowship program director at New York University School of Medicine who wrote an accompanying editorial to Conant’s study, this research touched on important questions that have hovered around breast cancer screening.

“Conant and her colleagues’ study is a much-needed, relatively long-term evaluation of tomosynthesis over multiple breast cancer screening rounds. It’s the first to show that the cancers detected by sustained tomosynthesis screening may be more aggressive than cancers detected by 2D mammography,” she told Diagnostic Imaging. “These are the kinds of breast cancers that we would like to be able to detect early.”