Chemobrain Introduction: When Cancer Treatment Disrupts Your Thinking and Memory skills

Mayo Clinic Staff

October 15, 2004

For years people undergoing cancer treatment described their minds as being in a fog — unable to concentrate and remember details important to their everyday lives. Doctors and researchers knew something was wrong, but they couldn’t put their fingers on what it was.

A growing body of research shows that what those people were experiencing is called cognitive impairment — the loss of the ability to remember certain things, learn new skills and complete certain tasks. The cause of cognitive impairment during cancer treatment still isn’t clear, nor is it clear how often it happens or what may trigger it. Doctors aren’t sure what they can do about it.

But that doesn’t mean there isn’t any hope. Recognize cognitive impairment and its association with cancer treatment, and talk to your doctor about your symptoms or concerns. Taking small steps can help you cope with changes in your memory during treatment.

What is chemobrain?


You may have heard the terms chemobrain and chemofog. These terms refer to cognitive changes during and after cancer diagnosis and treatment. Women with breast cancer who underwent adjuvant chemotherapy were the first group to bring these symptoms to light, as more started mentioning their symptoms to their doctors. It isn’t clear whether chemotherapy, or other factors such as stress and hormonal fluctuations, cause the changes in memory and thinking. What is clear is that some people with cancer do notice increased difficulties with certain mental tasks after cancer treatment.

In general, researchers have found that chemotherapy can affect your cognitive abilities in the following manners:

bulletWord finding. You might find yourself reaching for the right word in conversation.
bulletMemory. You might experience short-term memory lapses, such as not remembering where you put your keys or what you were supposed to buy at the store.
bulletMultitasking. Many jobs require you to manage multiple tasks during the day. Multitasking is important at work as well as at home — for example, talking with your kids and making dinner at the same time. Chemotherapy may affect how well you’re able to perform multiple tasks at once.
bulletLearning. It might take longer to learn new things. For example, you might find you need to read paragraphs over a few times for the message to set in.
bulletProcessing speed. It might take you longer to do tasks that were once quick and easy for you.

About 20 percent to 30 percent of people undergoing cancer treatment will experience cognitive impairment, though some studies report that at least half the participants had memory problems. Signs and symptoms of these memory changes last for at least a year or two after your treatment. The changes can continue for several years or they can go away sooner.

Changes in memory during and after treatment may be very subtle. You might notice changes during your everyday tasks and as you start working again after treatment. The memory changes are often so subtle, in fact, that researchers find that people who report having memory difficulties tend to score in the normal ranges on tests of their cognitive ability. That makes it more difficult to understand, diagnose and treat the memory changes.

What causes the memory changes?


Doctors don’t know what causes the cognitive changes associated with chemotherapy. It was previously thought that chemotherapy drugs didn’t enter your brain, but were rejected by the blood-brain barrier, which separates things that should be in your brain from those that shouldn’t. But some researchers now suspect some chemotherapy drugs may be able to slip past the blood-brain barrier. This could potentially affect your brain and your memory.

It isn’t clear which chemotherapy drugs are more likely to cause memory changes or if higher doses pose a bigger risk than do smaller ones. And it isn’t possible to predict who’s more likely to have cognitive impairment after chemotherapy.

A number of factors can cause temporary memory problems in people undergoing chemotherapy — making it difficult to decipher the so-called chemobrain from the normal stresses of treatment. Temporary memory problems can, for the most part, be treated. Causes include:

bulletLow blood counts. If your blood counts are low, you might feel tired, making it difficult to concentrate.
bulletStress. Being diagnosed with cancer and starting treatment is stressful. Stress also makes concentrating difficult.
bulletMedication to treat side effects. Certain medications for treating side effects such as nausea and vomiting may cause drowsiness. When you’re tired, it may take longer to complete tasks.
bulletLingering depression. Depression is common in people with cancer. If your depression continues after your treatment, you might find it difficult to pay attention.
bulletLingering fatigue. Fatigue is a side effect of several types of cancer treatment, including chemotherapy. Your fatigue might end when your cancer treatment ends, though it also can continue after treatment.
bulletHormonal changes. Many cancer treatments may alter the normal hormonal balance in your body, causing cognitive changes. Hormonal changes are a side effect of some treatments and, with other treatments, are the intended way to treat your cancer.

Talk to your doctor about your memory problems. If your symptoms are caused by medications or stress, your doctor can treat those symptoms and help get your mind back on track.

How are memory changes treated?


If you have impaired memory, your doctor may first try to rule out any other causes of memory problems, such as stress and depression. Currently no medications exist to treat cognitive impairment associated with cancer and its treatment. Researchers are investigating whether medications for such disorders as depression, attention-deficit hyperactivity disorder (ADHD) and dementia could prove effective.

You can help yourself cope with the changes in your memory by taking a few simple steps. You might want to:

bulletExercise your body. Aerobic exercise helps your mood and can make you feel more alert. Both can help you when it comes to concentrating.
bulletExercise your mind. Give your mind a workout by learning a new skill, such as a new language. Take a class or participate in a book club.
bulletTrack your memory problems. Keep a detailed diary of your memory problems throughout your day. Carry your diary with you and take quick notes on what medications you take and when. Note the time of day your memory problems occur and the situation.
bulletTarget specific problems. Use your daily diary to determine what influences your memory problems. If they tend to crop up in the early afternoon, you can prepare yourself by not scheduling meetings or deadlines at that time of day.
bulletTake notes. Make a list of everything you need to accomplish today and use that as a guide. Take detailed notes of things you need to remember.
bulletStart a routine. Put your keys or other commonly misplaced objects in the same place every time you set them down. Try to keep the same schedule every day.
bulletTalk about your problems. Be open with your friends and family about what you’re experiencing. Let them know your mind is moving a little slower these days and explain how they can help you. This can make you more relaxed and make it easier for you to think and process information.

Find the coping method that’s best for you and stick to it. Talk to your doctor about your concerns. He or she might have some other suggestions.

What other types of cancer treatment might cause cognitive impairment?


Chemotherapy isn’t the only cancer treatment that may cause memory and thinking problems. Other treatments that might affect your brain include:

bulletHormone therapy. It isn’t clear whether women undergoing hormone therapy that alters the amount of estrogen in their bodies experience memory problems. Some studies link memory to the amount of estrogen in the brain. Other studies haven’t found this link.
bulletImmunotherapy. This experimental therapy stimulates your body’s own defenses to fight your cancer. Treatment with cytokines — a type of protein that causes inflammation in your body — may cause problems with memory, multitasking and processing information.
bulletRadiation therapy. Radiation to your brain can impair your memory and your motor function, as well as your ability to learn new things and to multitask. Older adults and people receiving high doses of radiation are at a greater risk of memory problems. If you receive both chemotherapy and brain radiation, your risk is also higher.

As research continues doctors will be able to better understand which cancer treatments cause cognitive impairment and what they can do to limit their side effects.

Take note of any memory problems


If you’re currently undergoing cancer treatment or you’ve already been through treatment, take note of any problems you have remembering certain things or concentrating during certain tasks. Talk to your doctor about your signs and symptoms.

If you’ve yet to start your treatment, talk to your doctor about the risks of treatment, including cognitive impairment. Understanding your risks can help you make more informed decisions about your treatment.


Chemobrain – Real Or Fiction?

Rachael Myers Lowe,

June 21, 2004

Fuzzy thinking, difficulty learning new things, trouble recalling words or remembering details and focusing attention have been associated with chemotherapy in previous studies of breast cancer patients. A new study of breast cancer patients by researchers at the M.D. Anderson Cancer Center in Houston questions the validity of the earlier research and concludes earlier reports “may have overestimated the true incidence of decreases in cognitive functioning secondary to chemotherapy.”

Writing in the August 1 issue of Cancer, a publication of the American Cancer Society, Christina A. Meyers, Ph.D., and colleagues report that 35% of the women in their study had mental impairment before they began systemic chemotherapy. Taking a measure of cognitive function before adjuvant chemotherapy was administered was not done in the previous studies.

“Given the current documentation of objective cognitive impairment before adjuvant systemic therapy, a large portion of patients in previously published reports who performed at levels below what was expected when they were assessed after chemotherapy may well have performed at that same level before chemotherapy,” the authors write.

Is chemobrain is a fiction?

“Absolutely not!” Meyers told

Meyers says she has another study recently published that tested women before they had treatment, while they were on treatment, and a year after treatment had stopped.

“Sixty percent of those folks declined on chemotherapy so chemo brain is for real   It’s just that it’s not a simple as that, not that it was ever simple. There’s also cancer related aspects to take into consideration and then there’s the aspects of the person themselves, susceptibilities or vulnerabilities in certain people to develop these symptoms,” she said.

Perhaps chemobrain is a bad name. The issue of cognitive impairment in cancer patients may be caused by many factors: a patient’s genetic makeup, nutritional factors, immune system, hormonal history, reduced “cognitive reserve” may increase cognitive impairment. The cancer itself may also contribute to development of cognitive dysfunction.

In the study detailed in Cancer, Meyers and colleagues studied the mental functioning of 84 women who had been diagnosed with breast cancer but had no evidence of metastatic disease.  They all were older than 18 years of age (on average nearly 51 years old), had completed more than 8 years of formal education (14 years was the average), and spoke fluent English. None of the patients had a previous history of depression, earlier cancer, or were taking any substances that would affect the central nervous system. All patients had either undergone surgery or a needle biopsy before the mental function tests were given. Some of the patients had used hormone replacements therapy (HRT); some had undergone adjuvant radiotherapy.

They were all given a battery of tests, before adjuvant chemotherapy began and after, to measure attention, memory, language, executive function, visual and motor skills, depression, and anxiety.

Going into their treatment, 35% of the women registered at least one measure of cognitive impairment; 26% reported some symptoms of anxiety or depression.  Women who reported anxiety or depression were much more likely to experience impaired cognition of some degree pre-chemotherapy.

Compared to what’s considered normal, pre-treatment women with breast cancer experienced the greatest impairment to verbal learning and verbal memory.  Other impairments were less pronounced.

The researchers said some trends, while not statistically significant, were worth further investigation: patients who underwent more invasive surgery (lumpectomy versus mastectomy), patients who were postmenopausal, and patients who had not previously used any HRT appeared to be at greatest risk of pre-treatment cognitive impairment.

The bottom line is more research needs to be done that measures cognition before and after treatment. The authors say doctors should continue to counsel their patients on cognitive functioning and refer them to specialists if they or their families report changes in the patient’s ability to think.

Is mental impairment common in other cancers? Meyers says she has found it in newly diagnosed but untreated small-cell lung cancer patients and leukemia patients.


bulletCancer August 1, 2004. Published online June 21, 2004.
bulletcancerpage telephone interview with Christina Meyers, 6-21-04

ChemoBrain/Cognitive Dysfunction

Tara Parker-Pope, The Wall Street Journal, April 6, 2004

For years chemotherapy patients who complained of memory problems — or so-called “chemo brain” — were told it was all in their head. But new research shows that chemo brain is real.

While cognitive complaints following chemotherapy have often been written off to depression, anxiety and even menopause, doctors now know that chemotherapy can trigger real — and sometimes lasting — changes in a patient’s brain. Last week, researchers from University of California-Los Angeles presented imaging studies at a scientific meeting in Orlando, Fla., showing marked differences in the brains of breast-cancer patients who had undergone chemotherapy compared to patients who had undergone surgery alone. Studies are just beginning on whether certain drugs or cognitive therapy can help prevent or offset that side effect. Some patients are given the stimulant Ritalin, which can help improve concentration.

Not every patient develops cognitive problems after chemotherapy, but enough people do that more and more doctors are beginning to warn patients about the potential side effect, says Eric Winer, director for breast oncology at the Dana-Farber Cancer Institute in Boston. Most of the problems typically relate to focus, fast thinking, organization skills and an inability to multitask.

The problem has been most studied in breast-cancer patients, in part because many of those patients are relatively young and highly educated and have high survival rates. That makes cognitive declines more noticeable compared with declines in older or retired patients. But cognitive problems have also been noted in other cancers, including lymphoma and lung cancer.

Much more research is needed to say conclusively how widespread the problem is. Studies of breast-cancer patients show that nearly two-thirds of women treated with chemo develop some level of cognitive problems, though most recover on their own in the weeks or months after treatment stops. Still, as many as 20 percent to 25 percent of patients may develop lasting problems, says Tim A. Ahles, program director of the center of psycho-oncology research at Dartmouth Medical School, which has led much of the research on the subject.

For patients, the simple acknowledgment that their complaints are real has been a long time coming. Houston resident Janis Shea, a nurse and former college professor, says that after undergoing chemotherapy for breast cancer, she began having trouble finding words and balancing her checkbook. Even her sense of humor was off. She recalls a friend telling a joke about shoes made from bananas. The punch line — “slippers” — was lost on her.

“Everybody was laughing, but I just didn’t get it,” she says. “I used to teach and lecture to 200 people and I was having trouble putting sentences together.”

Ms. Shea attended a support group and discovered other women were hesitant to talk about the problems out of fear it would jeopardize their careers or because their doctors didn’t think the problem was real. Ms. Shea’s complaints prompted her husband, a physician at the University of Texas M.D. Anderson Cancer Center, to discuss the issue with colleagues, who began research into the problem as a result.

But studying the ailment is tough. Some of the symptoms, such as short-term memory problems and loss of verbal fluency, can also happen during menopause, when estrogen production begins to plunge. Many breast-cancer patients are in the midst of menopause or thrown into it by the treatment. Memory problems also are associated with depression and fatigue, both common problems among cancer patients.

However, brain images show that in some people chemotherapy can trigger distinct changes. At UCLA, researchers studied the brains of breast-cancer patients who complained about cognitive problems after chemotherapy — comparing them to women with breast cancer who didn’t receive chemo. In the women who had undergone chemo, the images showed differences in metabolic activity in the parts of the brain involved in language; some parts of the brains of chemo-treated woman looked 25 years older than they were. Knowing that real changes have taken place in the brain has actually helped many women cope, says Dan Silverman, head of neuronuclear imaging at UCLA. “They say, ‘Now I know I’m not crazy,” he says.

In studies at M.D. Anderson, patients were given neuropsychological assessments both before and after chemo, and about 60 percent showed significant cognitive decline after treatment. It’s important to note that even though the problems are frustrating, they typically are subtle and manageable, says Christina Meyers, professor of neuropsychology at M.D. Anderson, where several studies are underway.

Dr. Meyers says the neuropsychological tests can reassure patients by ruling out Alzheimer’s, and help them better understand whether the problem is related to chemo, depression or other issues.

Researchers at Dartmouth University are studying “cognitive rehabilitation” for chemo patients, focusing on compensation strategies, such as writing detailed notes or using a hand-held organizer, as well as relaxation techniques, because cognitive problems increase with stress. At M.D. Anderson, some patients take Ritalin to help them focus, but researchers also are studying whether giving the anemia drug Procrit before chemo can prevent cognitive damage.

For patients who need chemo, the problems aren’t significant enough to turn down treatment. But doctors say patients who are borderline candidates may want to factor the potential cognitive side effects when deciding whether to undergo chemotherapy.