Marcia Frellick

December 01, 2015

CHICAGO — The detection of breast cancer is better with digital breast tomosynthesis, which creates a 3-dimensional picture using x-rays, than with standard mammography, results from a 3-year study indicate.

There was also a decrease in the interval cancer rate with digital breast tomosynthesis, "suggesting that it detects more clinically significant interval cancers," study investigators report.

Results from the 3-year study were presented by Emily Conant, MD, chief of breast imaging at the Hospital of the University of Pennsylvania in Philadelphia, here at the Radiological Society of North America 2015 Annual Meeting.

Previous research has shown that screening outcomes are better when tomosynthesis is added to digital mammography; however, those studies followed patients for only 12 or 18 months.

To determine whether outcomes are sustainable over time, Dr Conant and her colleagues looked at outcomes in their clinic population over 3 years.

The team screened more than 33,000 patients after the clinic converted to tomosynthesis in 2011. During the 3-year study period, they compared 12-month recall rates, cancer detection rates, positive predictive values, biopsy rates, and interval cancer rates with rates when the clinic was using digital mammography alone.

Fewer Recalls, More Cancer Detected

There was a significant reduction in recall rates from the baseline of 10.4% before conversion to tomosynthesis to recall rates in year 1 (P < .001), year 2 (P < .001), and year 3 (P < .003) after conversion.

There was an increase in cancer detection rates from the baseline of 4.6 per 1000 screened to 5.5 in year 1, 5.8 in year 2, and 6.1 in year 3, although the increase was not significant (P = .108).

There was a continuous increase over time in positive predictive values — the number of cancers per recalls — from baseline to years 1, 2, and 3, and the trend in year 1 was significant (P = .025).

The biopsy rate remained relatively stable from baseline to year 3.

That is a useful modality for annual screening and not just for one-time use.

There was a decrease in the interval cancer rate from the baseline rate of 0.9 per 1000 screened to 0.5 for year 1 and 0.1 for year 2. The rate for year 3 could not be determined because follow-up was inadequate.

The success over 3 consecutive years demonstrates that tomosynthesis is useful for detecting not only prevalent cancers, but incident cancers, said Tova Koenigsberg, MD, chief of the division of breast imaging at the Montefiore Einstein Center for Cancer Care in the Bronx, New York.

"That makes it a useful modality for annual screening and not just for one-time use," she told Medscape Medical News.

Tomosynthesis has been shown to be most useful in decreasing the recall, or false-positive, rate. And the cancer detection rate is higher with tomosynthesis than with standard mammography, Dr Koenigsberg reported.

However, although many centers have begun to adopt tomosynthesis for screening, it is not routinely used across the country, she said. These findings make the case that tomosynthesis is more sensitive than standard mammography, but the study does not address the issue of cost.

"This study is very interesting, since most centers haven't had tomosynthesis for that long," Dr Koenigsberg said. These data should reassure clinicians that it "will continue to be useful in the long run."

Revolutionizing Breast Imaging

Digital breast tomosynthesis "is definitely revolutionizing breast imaging," said Liane Philpotts, MD, professor of radiology and biomedical imaging at Yale University in New Haven, Connecticut.

The US Food and Drug Administration has approved tomosynthesis equipment from three manufacturers — Hologic, GE Healthcare, and Siemens — and there are more in development, Dr Philpotts pointed out.

Most studies so far have focused on screening capability, she said, but tomosynthesis also helps localize and characterize lesions.

Because there are fewer recalls and because many of those recalled will go directly to ultrasound, the diagnostic pool of patients is smaller with tomosynthesis.

Future studies will measure its ability to lower costs and reduce mortality over time; however, at the moment, insurance coverage for tomosynthesis is spotty because some carriers consider it investigational, she added.

"Currently, 39% of insured lives do have coverage," said Dr Philpotts. "We are getting there, but there's a ways to go."

Dr Conant reports serving as a speaker and being on the advisory board for Hologic and serving as a consultant for Siemens AG. Dr Koenigsberg and Dr Philpotts have disclosed no relevant financial relationships.

Radiological Society of North America (RSNA) 2015 Annual Meeting: Abstract RC215-02. Presented November 30, 2015.


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