Behavioral Psychologist Tim Ahles Discusses Cognitive Changes Associated with Cancer Treatment

Pictured: Tim Ahles

Behavioral psychologist Tim Ahles

With the number of cancer survivors in the United States at nearly 14 million according to the National Cancer Institute and cancer survivors living longer than ever, researchers are increasingly studying the long-term side effects of cancer and its treatments. One of those side effects is cognitive change — including problems with memory and concentration. Cognitive changes can significantly diminish a person’s quality of life after cancer treatment.

An article by a team of Memorial Sloan Kettering investigators, published in October in the Journal of Clinical Oncology, examines what is known about the causes and effects of these cognitive problems and reviews the current “state of the science” in this growing field.

Tim A. Ahles, a Memorial Sloan Kettering behavioral psychologist and the article’s lead author, spoke about what researchers found in a recent interview.

How common are cognitive changes?

It’s not uncommon at all for people to experience cognitive difficulties when they’re in active treatment for cancer. There are a lot of reasons for that: They don’t feel well, they’re tired, they’re anemic, and they may be taking sedative medications. The majority of patients in the middle of treatment report issues such as loss of short-term memory, difficulty concentrating, and inability to multitask.

Recovery happens slowly, but following treatment, most people do report improvements. About a year after treatment, between 75 and 80 percent say that their cognitive function is back to normal. (1)

Although most people recover, there are still millions of survivors whose cognitive function may never completely return to what it was before cancer. These deficits might affect someone’s ability to return to work or complete their education, and they can impact quality of life in many other ways.

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The problems you’re talking about are often called “chemo brain,” but are they caused only by chemotherapy?

No. If you look at the typical treatment for breast cancer, for example, it involves at least one surgery with general anesthesia, and also chemotherapy, radiation therapy, and hormone therapy. So when we say we’re studying the effects of cancer treatment, we’re really looking at the whole package. We’re not able to separate out one component of the treatment from the others.

We know that estrogen is important for memory function in women, so it makes sense that breast cancer patients who are treated with drugs that affect estrogen levels, such as tamoxifen and aromatase inhibitors, are likely to have problems with memory. In the same way, testosterone is critical for cognitive function in men, and men with prostate cancer who are given hormone-blocking drugs commonly have cognitive difficulties.

Of course, for patients with brain tumors, problems can also be caused by the location of the tumors themselves, and by surgery and radiation treatments in areas of the brain that may directly influence these functions.

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How do cancer treatments affect the brain?

That’s something we’re still figuring out. Most chemotherapy drugs do not cross the blood-brain barrier, but some do, so there may be some direct effects on the brain. Even if they don’t cross the barrier, the drugs may cause something called oxidative stress. This process creates molecules called reactive oxygen species that do cross the barrier and can be toxic to the brain.

Most chemotherapy drugs damage DNA, and we know that the accumulation of DNA damage can lead to changes in the brain. Chemotherapy also triggers the production of cytokines, small signaling molecules that can have an effect on the immune system and other regulatory systems in the body.

We’re also considering the effects of radiation therapy, even if it’s not administered near the brain. Like chemotherapy, radiation can damage DNA and cause changes in the immune system.

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What studies are being done to learn about the relationship between cancer treatments and cognitive change?

One area that’s very important is brain imaging. A number of studies have shown actual changes in brain structure and function in patients following cancer treatment. We have an imaging study going on now that follows breast cancer patients throughout treatment. We image their brains before treatment and then again during and after treatment to try to pinpoint when and where changes are occurring.

Animal models are also useful because we can give each treatment separately to sort out the effects that each one has independently on the brain.

Because much of the research in this area has been done in breast cancer patients, we are also expanding into other types of cancer, especially those that affect men and women equally. We and others have done research in lymphoma, and there is a group in Australia studying patients with colorectal cancer.

Finally, we need to do more to understand the cognitive effects of cancer treatment within the context of aging. Aging naturally reduces cognitive function, particularly memory and concentration, so it makes sense that age might make some people more vulnerable to long-term changes. So far, much of the research has been done in younger cancer patients, and we’re trying to get more data on adults aged 60 and above.

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What has research taught us about how we can treat or prevent these problems?

There are two main approaches right now. One is related to medication, looking at stimulant drugs like methylphenidate (Ritalin®) and modafinil (Provigil®). There is evidence that these drugs are effective for some people.

The other approach is developing more cognitive interventions, where people are taught new skills and ways that they can compensate for their deficits. Elizabeth Ryan, a neuropsychologist at Memorial Sloan Kettering and one of the coauthors on our paper, is looking at computer-based methods for treating cognitive problems in breast cancer patients.

Unfortunately we don’t know enough yet to be able to prevent cognitive problems from occurring, and this is a big part of why research is so important.

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What services are available for cancer patients experiencing cognitive changes?

Specialists on our Neuropsychology Service can perform cognitive testing to assess your cognitive skills and symptoms, help clarify the most likely cause of cognitive changes, and recommend tactics for coping with changes.

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The research in the Journal of Clinical Oncology paper was supported by the National Cancer Institute of the National Institutes of Health under award numbers CA87845, CA101318, CA129769, and CA132378.


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I was so glad to learn of your recent studies. I am a 2 time survivor of systemic lymphoma and 2 time survivor of CNS lymphoma. I am currently undergoing an autologous stem cell transplant right here at Sload Kettering under the direction of Dr. Craig Sauter. This is my second auto-transplant in all. Obviously cognitive issues are a major concern for patients like me and for the many brain tumor patients that I am in contact with in the form of on-line support groups. I understand that your current studies are focused on breast cancer and soon to include colorectal cancers. Seeing this article made we want to reach out and say that, if the time comes that you want to do some studies on brain tumor patients, there is nothing I would not be willing to to help. I also have access to many, many others in support groups that would be willing to assist in any way with this cause. Thank you very much for adding this issue to your many studies being performed here at Sloan Keterring. I truly believe that I am receiving the best healthcare in the world here at Sloan Keterring.

Thank you for your comment! We will forward this to Dr. Ahles.

I participated in Dr. Ryan's study. I also sat in the audience as a patient advocate while research was presented in San Antonio attempting to attribute much of the problems to sleep issues. It caused quite an uproar on social media. I always tell people "Google Tim Ahles" and if he signed off on it, you KNOW it's reliable. I echo the sentiment of Arthur Baker. I KNOW I received the best care. I'm five years post "active treatment" and my brain STILL isn't back to normal. Although I've resisted the provigil route, it's becoming enough of a problem that I may break down and try it.

AnneMarie, I have been on Nuvigil for about a year, and it did seem to be effective with daytime drowsiness, at least for a while. It is an expensive drug, even with insurance coverage (my co-pay is $50 for 30 pills). My prescription just expired, and must be re-authorized after one year, so I thought I would try to go without it. It doesn't seem to be working out, and I will probably have to go back on it, since taking a two or three hour nap most afternoons is quite annoying. My short term memory was never improved with it, but at the same time, it didn't deteriorate, and a lot of that probably has to do with my age (64). I have found that since I stopped taking it, my focus and concentration are starting to diminish, for whatever that's worth, so I guess I will just have to bite the financial bullet and start taking it again. One suggestion, should you start taking any of these drugs, is to not take them at night. Nuvigil is a one pill a day dosing. I believe Provigil is, as well. I have not experienced any noticeable side effects from the Nuvigil, other than the hit to my wallet. :-)

Thank you, Bill! If I didn't have PCCI (I'm enjoying that new terminology: post cancer cognition impairment), I would have remembered to check the "notify me" box below.


i understand breast cancer is a big problem but it seems to me lung cancer is on the back burner i have chemo brain i am 69 had surgery 41/2 years and had 16 chemo treatments please my neuropthy is getting worse and my chemo brain also i have just 1.25 lungs and am handicapped what can be done to help put lung cancer out front.

I have had breast cancer and a double mastectomy (2008). However, my cognitive impairment is most likely the result of a brain injury sustained in a car accident (2003, diagnosed several years later). I have taken Provigil and it definately helps with fatigue - no naps in the afternoon. I am taking Namenda to help with cognition and to prevent migraines. I don't know whether drugs help or after a period of time coping mechanisms are learned to deal with the loss of short term memory etc. I suspect a little of both. I don't know what I would do without my IPhone with it's calendar, contacts and notes features. I have not experienced any side effects from these drugs. Talk with your doctor or a neurologist. Good luck.

My Daughter Debbie is a survivor(10 yrs) of anaplastic astrocytom grade 3.She had surgery,8 months of temador,6 weeks of daily radiation.She suffers from cognitive dysfunction,fatique,cannot multitask,& short term memory loss.I feel that she is getting worse as the years go by.She lacks common sense.She was prescribed provigil a few yrs.ago & it was not covered for her.FDA only approved certain illness for it and not for brain cancer.It also is very expensive.I truly don't know where to turn for help for her.She is now in Florida & I pretty much have to be her brain.Her doctors were from Sloan Kettering in N.Y.

Our son is a 13 year brain tumor survivor. Provigil helped tremendously. We cannot get it now because our insurance with is a traditional type of policy will not pay for it. I understand what the mom is saying about her daughter Debbie. Late effect clinics just don't do the job. Our son is now 16 and a clinic with a dietician, psych, social worker, etc., just doesn't help in the day to day with school and social life and no direction is given with regard to 2nd cancers. Cognitive studies of children will not show 80% recovery.

I am surviving lymphoma . I have had two bone marrow transplants,etc. For me cognitive disfunction has been incredibly frustrating. I started making my own therapy so I can compensate for what I no longer am as sharp anymore.I lose words and sentences often fall apart and I get lost. I have not found interferance with ideas.As a matter of fact i like the different forming of the them and use them to move thoughts in other ways.One way I have used to get there is to challenge myself and other people. I first started with mind games. I find trading ideas with friends who accept my new idiosyncrasies very helpful.I have lived a creative life that now manifests itself in a slightly different manner.I believe that is what people must try because being mentally idol will destroy you. It is about curiosity. I do wonder what the future holds as far as medicines are developed.I am pleased that research is moving on. I love science and the dedicated people who make it thier life. Yes my fellow cancer folks, some days really suck. Sometimes it is weeks.But it is yours. So make the most on good days. My best wishes to all. Peace.

I am an 8 year breast cancer survivor and definitely experienced a loss of cognitive function. Because the chemotherapy put me into menopause, I am wondering how much of the changes were from the chemotherapy and how many were related to menopause. The "searching for words" isn't as bad as it was, but it certainly is still there, and my friends and family have learned that is just a part of my life now, however the memory loss was very frustrating to all of us and I hadn't been prepared for that.

I have Leiomysarcoma / uterine sarcoma. I have had surgery, radiation, 2 years of chemo and am now on a maintenance chemo program for life. I am also an accountant still working. I know my short term memory and ability to concentrate and multi task have been affected. I am worried I will have to stop working because I can't perform my job at the same level. I have not talked with my Dr. concerning this as she seems only concerned with chemo treatments and tumor size. These are very important but side effects of chemo include brain functions.
I am happy to hear there is research concerning "Chemobrain", as it is a real problem for me in coping with chronic cancer.(I thought I made up that term) I just wish you would do more research on other cancers besides breast cancer or prostate cancer. Will what you learn concerning breast cancer patients help other cancers?

Hi, Eileen. We spoke with Dr. Ahles about your question, and he said, “The research examining cognitive changes associated with chemotherapy for breast cancer is broadly relevant to individuals who receive chemotherapy for other types of cancer. However, there may be differences as well based on the type and doses of chemotherapy used. Fortunately, there are a growing number of studies examining cognitive changes associated with chemotherapy treatment across the spectrum of cancer types. I anticipate that the results of those studies will be published over the next one to three years.” Thanks for your comment.

I'm a lymphoma survivor. I had radiation 25 years ago and chemo 22 years ago. I've also had 3 hip replacements and a broken femur from osteonecrosis, a side effect from my chemo. I'm only 55, but over the years my cognitive function has gotten worse and worse. I understood that the chemo was the beginning and now, thanks to your article, I'm guessing the multiple surgeries are probably a factor in my recent deterioration.

Thanks so much for your research report. I have not been able to get such a definitive statement from my oncologist, for whom I have the utmost respect. I am a five-year survivor of fallopian tube/ovarian cancer and am 66 years old. After taxol-carboplatin treatments following surgery, I suffered horrific chemo-brain and neuropathy. The neuropathy has abated somewhat, not totally. My search for specific words, then a search for an alternative word, is very frustrating still. My immune system is still very weak. Fatigue remains a big problem because---in part---my red blood cells never recovered. I'm sure part of the problem is that I had to immediately stop my hormone replacement therapy. But the rest is due to residual side-effects. I wonder how much is related to the fear of recurrence---a very real problem for me. That would be hard to measure, I suppose. But again, I thank you for your efforts.

I am so glad that we are researching an area of deep relevance to long time survivors such as myself (had Hodgkin's followed by chemo and radiotherapy in 1986-87). I founded CanSupport in 1996 and we run the largest home-based palliative care service for people with cancer in New Delhi, India. Recently, we have been asked for advice on how to mange a 67 year old woman with breast cancer recurrence who is receiving chemo and seems to have turned manic. She does not sleep, is aggressive, unpredictable and sedatives do not seem to work on her. Could this be "chemo brain" as well? Scans do not show mets to the brain.

Thank you for your comment. Unfortunately, we are not able to answer personal medical questions on our blog. We encourage you to speak with a local physician about this question.

very interesting article. I had in 2012 surgery and radiation to my face that went through to the back of my head due to a diagnosis of mucosal nasosinus melanoma. I have more difficulty with word finding and find that I cannot multitask so easily. for example i may understand and can see the image of what i want to say "fluid in the lungs so i say with a struggle, liquid in the lungs. interesting about the cytokines. thank you

Dear Judy, we are sorry to hear about the difficulties you have experienced as a result of treatment, but are glad that you found the information on this blog helpful. We wish you all our best and thank you for your comment.

My 78 year old mother has a metastatic brain tumor. She had full brain radiation in January and pin point radiation the end of May. At this time she is sleeping 20 out of 24 hours, barely walking, weak, often incontinent and confused about anything present day. Long term memory is intact. We are wondering if her cognitively ability will improve at all? What questions should we be asking? Thank you.

Dear Cindy, we are sorry to hear about your mother’s diagnosis. Her oncologist may be able to give you more insight on her prognosis and whether her cognitive ability might get better. We recommend that you ask whether there is anything that can be done to help regain some of her cognitive abilities and/or improve her physical condition in general. Thank you for reaching out to us.

Can you give information about what the diagnosis of Mature B Cell Lymphoma means. A family member has been diagnosed with this.
Thank you.

We’re sorry to hear about your family member’s diagnosis. If you would like general information about the disease, we recommend that you contact the National Cancer Institute’s Cancer Information Service at 800-4CACNCER.

If your loved one would like to speak with someone about coming to MSK for treatment, he or she can call 800-525-2225 or go to for more information on making an appointment. Thank you for your comment, and best wishes to you and your family.