Two types of nuclear breast imaging scans may actually increase the risk of developing radiation-induced cancers, according to research published today in a special online report and in the October issue of Radiology.

Research conducted by Dr. Edward Hendrick, a clinical professor of radiology at the University of Colorado, Denver School of Medicine, found that single breast-specific gamma imaging (BSGI) or positron emission mammography (PEM) carries a lifetime risk of inducing fatal cancer greater than or comparable to a lifetime of annual screening mammography, starting at age 40.

“Not all breast imaging procedures carry the same doses and risks as mammography,” Hendrick told DOTmed News. “Physicians prescribing these studies need to be aware of the risk and inform the patients of those risks.”

Both procedures are nuclear imaging tests, injecting radioactive material into patients. In fact, the imaging agent used in BSGI is the same — and the same dose — as the one used in nuclear cardiac stress testing, explained Hendrick. He pointed out that researchers thought if the agent, technetium 99m–sestamibi, was used in other tests it would be safe in BSGI scans.

“But it turns out, it carries a considerably higher dose risk than most other breast procedures,” he said. “The risk is exactly the same between a stress test and BSGI. The point is, most breast imaging procedures, you’re irradiating the breast. The doses to other tissues are very, very minor. With these nuclear procedures, BSGI or PEM, the dose to the breast is relatively modest…but the dose to other organs is not modest by comparison.”

Hendrick, the sole author on the paper, reported that two-view digital mammography and screen-film mammography have an average lifetime risk of fatal breast cancer of 1.3 and 1.7 cases, respectively, per 100,000 women aged 40 years at exposure and less than one case per 1 million among women aged 80 years at exposure. Annual screening mammography in either digital or screen-film in women ages 40 to 80 was found to be associated with a lifetime risk of fatal breast cancer of 20 to 25 cases in 100,000. Dedicated breast computed tomography and digital tomosynthesis — neither FDA-approved — were found to have an average lifetime risk of fatal breast cancer of 1.3 to 2.6 cases, respectively, per 100,000 women aged 40 years at the age of exposure.

The cancer risks from BSGI and PEM were alarmingly higher. Hendrick found that a single BSGI exam was estimated to carry a lifetime risk of fatal cancer 20 to 30 times that of digital mammography in women aged 40 years, and the lifetime risk of a single PEM exam was 23 times greater than that of digital mammography.

Generally, BSGI or PEM exams are a follow-up to a mammogram, explained Hendrick. The scans are used similarly to the way MRI is used — as a diagnostic adjunct to mammography, not as a screening tool.

“Don’t start thinking about using these procedures for screening because they carry a far greater risk than mammography,” he said. “If you did annual screenings with these devices, you expose significant risk to the patient.”

The nuclear imaging tests are marketed especially to women with denser breasts because they can better detect abnormalities than conventional mammography, said Hendrick. But women with denser breasts are generally younger, and thus carry a greater risk of developing radiation-induced cancers.

But Dr. Marcela Böhm-Vélez, a member of the American College of Radiology, clinical assistant professor at the University of Pittsburgh and president of Weinstein Imaging Associates doesn’t use BSGI on women younger than 40 years old. Instead, she uses ultrasound as a complementary tool.

“I have been very conscious about whom to recommend BSGI to,” said Böhm-Vélez, who was referred to DOTmed News by Dilon Diagnostics, a camera manufacturer that conducts BSGI.

While manufacturers say these nuclear tests only administer 2 mGy of radiation to the breast, there is often greater exposure to other parts of the body, said Hendrick.

“They’re not telling you [what] the rest of the organs [are getting] and what those risks are,” he said. “[Manufacturers] are sweeping it under the carpet, to some extent.”

These nuclear tests may increase the risk of cancer in the intestines, kidneys, bladder, gallbladder, uterus, ovaries and colon, according to the report.

But the research only tells radiologists what they already know, said Böhm-Vélez, who recognizes that these nuclear tests should only be used as a diagnostic tool, and even then, cautiously ordered.

“Cardiologists use the stress test annually without thinking about how much radiation they’re giving [patients],” she said.

At this point, there haven’t been enough studies conducted to determine whether the nuclear tests are more accurate than conventional mammography, said Hendrick. But Böhm-Vélez swears by the test and its accuracy.

“In the right situation, when it’s used correctly, [BSGI] has been an extremely helpful tool for me,” she said.