TOMOSYNTHESIS USE FOR BREAST CANCER SCREENING?

For the first time, the National Comprehensive Cancer Network (NCCN) recommends that clinicians "consider" tomosynthesis as part of annual breast cancer screening.

The context of the recommendation is annual screening mammography in both average- and increased-risk women and refers to tomosynthesis as an adjunct to digital mammography.

The newly updated NCCN guide explains: "Multiple studies show combined use of digital mammography and tomosynthesis appears to improve cancer detection and decreased call back rates. Of note, most studies use double the dose of radiation. The radiation dose can be minimized by synthetic 2-D reconstruction."

Therese Bevers, MD, chair of the NCCN breast cancer screening and diagnosis panel, said that the recommendation is "based on both retrospective and prospective data that shows an increase in detection of breast cancers."

Dr Bevers, who is from MD Anderson Cancer Center in Houston, Texas, also noted that information about the evidence on call-back rates is not uniform. "More recent studies have shown an increase in recalls," she said in an email to Medscape Medical News.

"I think tomosynthesis is the mammography of the future," Debra Monticciolo, MD, a spokesperson for the American College of Radiology, said in an interview. Dr Monticciolo is professor of radiology at Texas A&M College of Medicine in Bryan and was not involved with the NCCN panel.

Dr Monticciolo explained that conventional digital mammography produces one image of overlapping tissue, while tomosynthesis provides multiple small pictures of breast tissue as the scanner moves in an arc.

The difference between images produced by tomosynthesis and conventional mammography has been described as being akin to a ball (3 dimensional) vs a circle (flat).

"Generally, it makes things easier to see," said Dr Monticciolo.

She said that nearly all (98%) of US mammography is now digitally based and tomosynthesis is also a digital technology. Most centers that have both tools perform standard digital mammography and add tomosynthesis to it in select patients.

The ACR does not have exact numbers on the mammography market share of tomosynthesis in the United States. But an estimated 25% to 50% of US mammography facilities have tomosynthesis units, said Dr Monticciolo"Tomo is popular, people are interested in it, but it hasn't been widely reimbursed," so that has slowed down investments in the units at centers, she said.

It is widely known that the NCCN and its guidelines influence insurers' coverage decisions. A press release issued after the NCCN guideline update by a public relations firm working for the tomosynthesis maker Hologic speculated the new endorsement will change some insurers' coverage.

"With these new guidelines…it's anticipated that coverage for breast tomosynthesis will be impacted on a wider scale as insurance providers have historically pointed to the guidelines as their reasoning for not covering the exam to date," reads the Hologic-sponsored press statement.

However, the US Preventive Services Task Force (USPSTF), another major organization that influences insurance coverage, recently did not endorse the technology.

In its 2016 update on breast cancer screening guidelines, the USPSTF concluded that the current evidence was insufficient to assess the benefits and harms of digital breast tomosynthesis as a primary screening method for breast cancer.

The organization made the same determination about tomosynthesis as an adjunctive screening for breast cancer in women with dense breasts.

Screening with tomosynthesis has not been proven to reduce mortality, which is the gold standard of evidence for screening interventions, said Dr Monticciolo.

"We don't have mortality reduction studies with tomo — that would take years and years," she said.

However, studies of tomosynthesis "consistently" show an increase in the breast cancer detection rate," she said. "We have found a 40% to 66% increase in detection of invasive cancers."

Tomosynthesis is a relatively new technology; the first machine (from Hologic) was approved in the United States in 2011.

But it has been highly touted. For example, Emily F. Conant, MD, chief of breast imaging in the Department of Radiology at the University of Pennsylvania in Philadelphia, called tomo "the most exciting improvement to mammography that I have seen in my career."

Dr Conant was the senior author of a 2014 study published in JAMA that showed digital breast tomosynthesis can locate significantly more (41%) invasive cancers than can conventional digital mammography.

However, in an accompanying editorial, Etta Pisano, MD, from the Medical University of South Carolina in Charleston, and Martin Yaffe, PhD, from the University of Toronto, Ontario, Canada, did not conclude that tomosynthesis should replace conventional digital mammography.

That question is best placed into a larger context — the debate about screening mammography in general, they argued.

The editorialists wrote: "The continuing controversy surrounding the most effective strategy for deploying the various available technologies continues unabated, and clear consensus is lacking on when to screen, how often, and with what tools, or even which screen-detected cancers could be managed more conservatively."