What You Need to Know About ‘Chemo brain.’

Cognitive changes while on treatment is not uncommon.



"Chemo brain is extremely common. As many as 75% of cancer patients have experienced it during their treatment. About a third of patients may continue to struggle after treatment."

- Dr. Arash Asher, Director of Cancer Rehabilitation and Survivorship at Cedars-Sinai.


For the majority of patients who overcome cancer, some treatment related side effects can be a lifelong companion. Some 17 million Americans have survived cancer, and the number is expected to grow to 20 million by 2026, according to the National Cancer Institute. It’s estimated that at least half of these individuals may suffer long-term effects from treatment that can impede their ability to work, succeed in school or other educational/vocational endeavors and even perform simple activities of daily living.


A majority of cancer patients get some combination of chemotherapy, radiation, immunotherapy and hormonal therapy as part of their treatment protocol. This often leads to cognitive impairment or what is known as the ‘chemo brain’. Of course, there are cancer patients who have cancer in the brain tissue itself who can suffer cognitive impairment due to the location of their brain tumor and associated treatments that directly affect brain tissue including surgery and radiation. However, the vast majority of cancer patients that suffer cognitive changes do not have direct brain involvement but rather it is a result of chemotherapy. It can affect people with different types of cancer and at different times. For example, people might notice changes at diagnosis (before treatment starts), during treatment and after treatment. It can affect men and women of all ages including pediatric cancer patients. Women may be more at risk than men. Genetic differences (small variations in DNA sequences in genes, called polymorphisms) may also increase risk. These occur in a variety of genes, not just cancer-causing genes.




The duration of ‘chemo brain’ symptoms ranges from short to long, with around one third of patients reporting side effects for months to as long as 5 to 10 years after the end of their treatments.

The cognitive changes from the direct effect of chemotherapy medications can be compounded by side effects of treatment including fatigue, anemia, nutritional deficiencies, constant pain related to cancer or treatment, using alcohol or other non-prescription drugs, sleep disturbances or hormonal changes, low mood, stress and anxiety. Cancer patients who are older and already have problems with memory, thinking, anxiety or depression have increased risk of suffering from cognitive issues.

Cognition, in simple terms, means the ability to perceive and react, process, understand, store and retrieve information.

It also refers to the ability to make decisions and produce appropriate responses. Cognition impairment or as it is commonly known in the cancer world as “chemo brain” describes changes predominantly in memory, attention, processing speed, and executive function. Studies suggest that short-term memory, working memory, and verbal ability are most frequently affected, followed by visuospatial memory, executive functions, and attention span. These deficits tend to be subtle, such that cancer survivors with chemo brain perform at the lower end of the normal range, but not yet in the pathological range of standard neurologic tests. This subtlety, together with the fact that standardized tests are designed to detect more severe, localized deficits such as traumatic brain injury, strokes, and dementia, means that these cognitive changes are often undetected or underestimated in the normal clinical setting.


Also Read : How to Manage Chemo Brain




Patients usually report:

  • Mild forgetfulness

  • Word-finding difficulties (searching for a word that's on the tip of the tongue)

  • Difficulty remembering dates, names, phone numbers, etc.

  • Trouble concentrating

  • Difficulty multitasking

  • Taking longer than usual to finish routine tasks


How do you know when forgetfulness is memory loss caused by aging or related to cancer treatment?

While the symptoms of memory loss and chemo brain are often similar, there are ways to tell them apart. These include:

  • Timing of Symptoms: Natural memory loss occurs slowly over the years and gets progressively worse over time. Chemo brain can come on more quickly, especially during or soon after treatment. In addition to forgetfulness, patients often say they have trouble multitasking or thinking as quickly as before.

  • Memory Recall: When prompted or given time to think it over, patients with chemo brain are often able to remember things they’re familiar with. But when patients have age-related memory loss or more serious memory disorders like Alzheimer’s or dementia, they are unable to recall basic information, even if they’re prompted or offered suggestions.

  • Difficulty in Talking: A patient with chemo brain will still recognize familiar objects and their names. Patients with memory loss disorders may use the wrong word for something or jumble their words.

  • Permanent Symptoms: The longer you’re exposed to chemotherapy, the more likely you may be to experience chemo brain. Unfortunately, age-related memory loss is typically permanent and may get worse over time.


Chemo brain symptoms and severity differ from person to person, your doctor can work with you to develop an individualized approach to coping.

It is important to understand that chemo brain is NOT dementia and ensuring that cancer patients have the best possible quality of life and suffer minimum side effects from their treatments should be part of the goals of treatment. The next blog will discuss the reasons for treatment related cognitive changes and how to deal with chemo brain. But the first step as always is to let your cancer care team know the moment you start experiencing any of the above mentioned changes, no matter how small or subtle these changes may be. Also, don’t hesitate to ask your family and friends for support and gentle reminders.

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Reason to Hope

Chemotherapy-driven estrogen loss is known to drive bone loss, but significant data suggests the
existence of an estrogen-independent mechanism of bone loss.  A new study in mice suggests
that a biological process known as cellular senescence, which can be induced by cancer
treatments, may play a role in bone loss associated with chemotherapy and radiation. These
findings may lead to treatments for therapy-induced bone loss, significantly increasing quality of
life for cancer survivors.
DOI: 10.1158/0008-5472.CAN-19-2348