Tim Mosenfelder / Getty Images Contributor

Sheryl Crow performs at the Mountain Winery on July 22, 2012 in Saratoga, Calif.

Singer Sheryl Crow says she believes her benign brain tumor was caused by frequent cellphone use, but the science to date does not support her theory.

Crow said that although no doctors will confirm it, she thinks it's possible her brain tumor, called a meningioma, is related to her cellphone use. "I [used to spend] hours on the old, archaic cellphones," Crow said on Monday's episode of Katie Couric's daytime talk show "Katie."

However, there is little evidence linking cellphone use to brain tumors, and most studies have not found a link. For one thing, brain tumors aren't any more common, although cellphone use has exploded.

"There is no conclusive proof that cellphones cause brain tumors," said Dr. Michael Schulder, vice chairman of the department of neurosurgery at Cushing Neuroscience Institute in Manhasset, N.Y.

About 6,000 people are diagnosed with meningiomas yearly in the U.S., according to the National Cancer Institute. Schulder told MyHealthNewsDaily that Crow falls into the group that is most prone to developing meningiomas — women in their 40s and 50s.

Although they're called brain tumors, meningiomas actually form in the lining of the brain rather than the brain itself. Most are benign, meaning they are unlikely to spread to other sites within the body.

"There is no reason to think that there's some other extra cause" for Crow's meningioma. "She meets the risk factor profile for developing that tumor," said Schulder, who is not involved in Crow's care.

Cellphones emit radiofrequency energy, which can be absorbed by tissues, according to the NCI. But so far, the only known biological effect of this energy, which is also emitted by microwave ovens, is a tiny rise in temperature, the NCI says. Unlike the ionizing radiation in X-rays, radiofrequency energy is not known to damage DNA. (Damage to DNA is considered a necessary step to cause cancer, the NCI says.)

A Danish study of nearly 2.9 million people that was published last year found that those who used cellphones for 11 years or more were no more likely to develop a type of benign brain tumor called a vestibular schwannoma than those who used cellphones for a shorter period, or not at all.

Another 2011 study from Denmark found no link between the location of brain tumors called gliomas and the regions of the brain that are exposed to the highest levels of radiofrequency energy.

In addition, between the 1987 and 2007, a period when cellphone use rose rapidly, there was no increase in the incidence of brain cancer in the United States, the NCI says.

A U.S. government study published last year did find that people who used a cellphone for 50 minutes showed an increase in sugar metabolism in the tissues on the side of their head closest to the phone. However, the health outcomes of this increased metabolism were not known, the researchers said. In May 2011, the World Health Organization said it was conceivable that cellphones might cause cancer.

Because cellphone technology is changing rapidly, and people use cellphones differently from in the past, more research is needed on the possibility of a link between cellphones and cancer, the NCI says.

In the meantime, Schulder said, people can use hands-free devices, such as headsets, to avoid unnecessary exposure to cellphone radiofrequency energy.

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When news broke that singer Sheryl Crow has a benign brain tumor called a meningioma, her representative swatted away concern by saying that “half of us are walking around with [a meningioma] but you don’t really know unless you happen to have an MRI.”

Well, no.

Despite that unnamed representative’s effort to make a brain tumor sound like a pimple, meningiomas are not anywhere near so universal, and, despite the “benign” designation, can be dangerous, leading to severe disabilities, and, in rare cases, death.

“About 2 to 3 percent are malignant,” Dr. Elizabeth Claus, director of medical research at the Yale School of Public Health, a neurosurgeon at Boston’s Brigham and Women’s Hospital, and the principal investigator for the multi-institution Meningioma Consortium, explained in an interview. “Then that is a very serious situation because there’s not much in the way of great treatments. They can metastasize, say to the lungs, and no chemotherapy will work for it.”

As the name indicates, a meningioma is a cancer of the meninges, the protective lining that surrounds the brain and spinal cord, often also called the dura.

Jason Merritt / Getty Images

Sheryl Crow, shown in 2011, announced she has a benign brain tumor called a meningioma.

It’s true that meningiomas are one of the most common types of brain tumors, comprising about one-third of all benign brain tumors, but meningiomas are not nearly as common as Crow’s rep would have you believe. As of 2005, approximately 138,000 Americans were known to have been diagnosed of meningioma.

However, explained Dr. Marc Mayberg, a neurosurgeon at Seattle’s Swedish Neuroscience Institute, “there may be many more, up to 10 times more patients but these people are unaware of it because the tumor is asymptomatic.” 

Sheryl Crow fits perfectly into the meningioma demographic. She’s 50, and rates of meningiomas are highest in middle-aged women.

Recently, medicine, which has focused on treating very deadly brain tumors like gliomas, has realized that it’s been giving benign brain tumors short shrift, so meningiomas have been the subject of renewed scientific interest.

Radiation to the head and neck is the only well-defined cause found so far. A study released last month from UCLA identified 27 cases of meningiomas over a 10-year-period that appear to have arisen following radiation to the head. While such treatments have usually been used to attack other cancers, “in the 1940s and 1950s,” Claus said, “kids were sometimes treated with radiation for all kinds of things, even ringworm, and those kids have a ten-fold increased chance of developing a meningioma.”  

A more common source of radiation may also spark meningiomas.

A study by Claus in the April issue of Cancer linked the tumors to dental x-rays. “Over a lifetime, cases were more than twice as likely as controls…to report having ever had a bitewing examination.”

Claus and her co-authors stressed that the elevated risk primarily resulted from X-ray exams “performed in the past, when radiation exposure was greater than in the current era.”

Studies of cell phone radiation have shown that use of the devices presents no increased risk of meningioma.

The fact that meningiomas are more than twice as common in women as in men, and that they have hormone receptors on their cells, may indicate that estrogen levels or progesterone exposures may also be involved with the tumors’ development. There’s a family association, too, so genetic heritage may play a role. 

The danger of meningiomas usually comes from the neural structures they can affect, often by pressing on neurons as the tumors grow. “Basically it is size and symptoms,” Claus explained. “The larger it is, the more likely to cause problems. It can actually be wrapped around the eye and you can lose vision. You can lose speech, and on down the list.” Meningiomas can affect one’s sense of smell, equilibrium, and physical strength.

Meningiomas are treated, or not, depending on how fast growing they are and what structures, if any, they are affecting. About half of people diagnosed with one require no treatment. Often, Mayberg explained, the tumor simply stops growing. Nobody knows why. When treatment is required, doctors typically opt for surgical removal, or radiation therapy to shrink the tumor.

According to Mayberg, the risk of recurrence depends on a patient’s age – the longer one lives the greater chance you’ll live long enough to have a regrowth – and how much of the original tumor was removed. If any tumor remains after surgery, the risk of recurrence is more than 20 percent.

Brian Alexander (www.BrianRAlexander.com) is co-author, with Larry Young PhD., of "The Chemistry Between Us: Love Sex and the Science of Attraction," (www.TheChemistryBetweenUs.com)  to be published Sept. 13.

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