Studies revive debate over 'chemo brain'

• About 20% of cancer survivors experience chemo brain long after end of therapy

Two new studies are reviving debate over the causes of "chemo brain," a mental fog that affects up to 75% of cancer survivors.

Cancer patients for decades have complained of feeling forgetful or mentally fuzzy, with many blaming toxic chemotherapy regimens. While the problem feels very real to patients, some doctors have dismissed the issue as imaginary.

Now, new research shows evidence of mental fog in women's brain scans.

A study presented last week at a meeting of the Radiological Society of North America found that chemo can cause brain changes that affect memory and concentration.

Researchers studied 128 breast cancer patients who complained of chemo brain, scanning their brains both before and after treatment, according to the study, presented by Rachel Lagos, a radiology resident at the West Virginia University School of Medicine.

Researchers used tests called PET/CT scans, or positron emission tomography, which captures brain activity by measuring how quickly it uses energy. CT scans, or computed tomography, use multiple X-rays to provide detailed pictures.

Lagos and her colleagues found declines in brain activity in areas involved with long-term memory, as well as problem solving, organizing and prioritizing. "Every single person showed change," Lagos says.

About 20% of cancer survivors complain of persistent memory problems, long after treatment ends, according to the National Cancer Institute. Patients with demanding professional jobs are more likely than others to complain of memory problems.

Scientists so far don't know for sure what might cause these symptoms.

Doctors such as Patricia Ganz, of UCLA's Jonsson Comprehensive Cancer Center, are studying the role of inflammation both in chemo brain and cancer-related fatigue. Her research has found that many women who complain of mental fog also suffer fatigue, depression and sleep problems.

A study by Tim Ahles, of New York's Memorial Sloan-Kettering Cancer Center, suggested that women may be more susceptible to chemo brain if they carry a form of a gene linked to Alzheimer's disease. It's also possible that memory problems and cancer have common risk factors, giving patients a greater chance of both.

Reaction to Lagos' study among breast cancers survivors has been dramatic. She received 800 e-mails from cancer survivors within a day of presenting her findings. Many were relieved that a doctor had confirmed their symptoms were real, Lagos says.

"People I'd never met where sharing their experiences. It was heartbreaking," Lagos says. For patients, being told that their symptoms aren't real "can be even worse than getting the diagnosis in the first place, because people think, 'Oh, I'm crazy.'"

A small study presented today at the annual San Antonio Breast Cancer Symposium, however, suggests that chemo may not be to blame for the women's memory impairments.

That's because women who complained of chemo brain had lower scores on memory tests even before treatment, says researcher Bernadine Cimprich, of the University of Michigan School of Nursing. Her study of 99 people used functional MRIs, or magnetic resonance imaging. Women diagnosed with cancer scored worse than healthy women in a comparison group, both before and after patients' treatment.

Her findings are consistent with earlier studies, which have found that 20% to 30% of patients have lower-than-expected scores, even before chemo.

Women who underwent chemo reported more fatigue than other women, even before receiving the drugs, Cimprich say. The more exhausted women felt, the worse their scores.

That suggests that at least some of the women's memory problems could have been caused by the stress and sleeplessness of being diagnosed with cancer, Cimprich says.

Studies show that other cancer therapies, such as a hormonal drug called tamoxifen, also can cause fatigue, according to the NCI.

Early menopause, which can be caused by chemotherapy or surgery to remove the ovaries, also can cause memory problems, says oncologist Claudine Isaacs, of Georgetown's Lombardi Comprehensive Cancer Center. Hot flashes caused by medications or early menopause can make women lose sleep, affecting their memory.

Cancer centers might be able to relieve women's symptoms by offering more psychological support, Cimprich says, as well as cognitive behavior therapy and mindfulness activities, which can include meditation. Exercise also has been shown to relieve fatigue and give people more energy.

Lagos says women can also cope with their mental fog by making lists and plans. For example, women in an earlier study felt overwhelmed by the task of organizing and cooking a meal.

But the same women were able to function much better after researchers gave them written menus, which helped the women focus their grocery shopping and meal preparation, Lagos say.

"It's critically important to understand the side effects of therapy and minimize them," Isaacs says. "We don't want women to say no to very important therapy because of this."