Wednesday, Dec. 15, 2010

Beware the hype on breast thermography

If the Internet buzz about a pain-free, radiation-free alternative to mammography sounds too good to be true, there’s a reason.

Breast thermography — recently touted as the “best breast test” by Oprah favorite Dr. Christiane Northrup, writing in the Huffington Post — has never been proven effective for routine breast cancer screening in a large-scale, randomized study. The FDA has never approved it for that purpose and in 2009 issued a warning letter accusing an Idaho health care provider of marketing thermography as a mammogram replacement.

Last year the Oregon attorney general shut down a troubled health clinic, accusing it of misrepresenting thermography as superior to mammography for breast cancer screening.

“The bottom line is that the proven technology for screening for breast cancer is X-ray or digital mammography. And that is the only proven technology,” said Robert Smith, director of cancer screening for the American Cancer Society.

Northrup wrote in the Huffington Post article that “many (doctors) believe that a mammogram is the best test for detecting breast cancer early … but it’s not.” She responded to a request for comment with an e-mail saying, in part, “Thermography has been shown to pick up abnormalities in the heat in the breast many years before a lesion would likely show up in a mammogram. The ideal is to use both technologies when appropriate.”

Breast thermography uses infrared cameras to detect subtle heat elevation associated with tumors, which tend to have more blood flow and higher metabolic rates than normal tissue. Thermography was considered a promising screening technology in the 1960s, but it fell out of favor with doctors in the 1970s when a large study found that it detected only 39 percent of breast cancers, while mammography picked up 78 percent.

Thermography advocates argue that the technology has improved vastly since then, and they may have a point.

A small study of thermography as a supplement to mammography, published in the American Journal of Surgery in 2008, found that thermography has an impressive 97 percent sensitivity rate, meaning that it correctly identified 97 percent of the women who had cancer.

Unfortunately, its specificity rate, the proportion of women correctly identified by the test as not having cancer, was a disappointing 44 percent. Modern mammography has a sensitivity rate ranging from 77 percent to 95 percent and a specificity rate from 94 percent to 97 percent.

The American Journal of Surgery study focused on a special population — women who already had suspicious mammograms or ultrasounds — and its authors speculated that that was the reason for the unimpressive specificity rate.

In a 2009 commentary in the journal Minnesota Medicine, Gregory Plotnikoff and Carolyn Torkelson wrote that thermography holds promise as a supplement to mammography — it’s FDA approved for that purpose — and called for more study. But they also raised concerns that some consumers were being led to think of it as a mammogram replacement, a “misconception” that “could raise public-safety issues.”

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