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Oncologist and clinical researcher Dr Nick Zdenowski discusses ‘chemo brain’ and how exercise can benefit cancer patients affected by the condition.


A recent research study conducted in the US has discovered that exercise can help breast cancer patients with ‘chemo brain’, a phenomenon that affects up to 75% of breast cancer patients whilst they are undergoing chemotherapy treatments.


Here, Dr Nick Zdenowski from Breast Cancer Trials discusses the study’s findings and explains their implications for cancer patients.


What is chemo brain?

Chemo brain is not easy to define because it affects people who have had chemotherapy for cancer in a variety of ways. Typically, it manifests as a mild but noticeable decline in cognitive functions, such as problems with short term memory, concentration and ability to find the right word or name.


“Typically, ‘chemo brain’ manifests as a mild but noticeable decline in cognitive functions”


Patients are often more aware of it than the people around them, making it difficult to measure. Generally, patients complain that they don’t have the mental stamina that they used to, or cannot multitask. They might find it more difficult to remember where they parked their car at the shops or to recall the name of an acquaintance. 


Whilst it is attributed to chemotherapy, there are a range of contributing factors, including the fact of the diagnosis of cancer (along with the psychological/emotional impact); having had surgery (and anaesthetic); and, in breast cancer, the hormone blocking treatments that are often given to patients. The end result is greater morbidity and even premature mortality.


Why does it happen?

We do not know enough about why chemo brain occurs. There are thought to be multiple contributing factors, including direct damage from chemotherapy to brain cells and their connections, damage to the microscopic blood supply of the brain, anaemia, physical fatigue and accelerated brain ageing. This lack of understanding, along with the variety of causes, makes the design and evaluation of prevention and/or treatment challenging.


Does it subside after treatment has finished?

Unfortunately, it often takes a long time to improve, long after chemotherapy has finished. It may continue to improve for up to two years following chemotherapy before plateauing.


Some patients never return to the same level of function that they had prior to their diagnosis and treatment. This has an impact on family and social function, as well as employability. We have research showing that women who have chemotherapy for early stage breast cancer are less likely to return to paid employment and, if they do return, they work fewer hours. The lack of effective treatments is a major challenge.


Do all patients suffer from it?

Not every patient has chemo brain and it presents along a spectrum, from very mild up to debilitatingly severe. Research suggests that during chemotherapy, up to 75% of patients experience some sort of cognitive problems. Many of those will improve substantially after chemotherapy is finished if they have a course of chemo for early stage disease. On the other hand, patients with advanced or metastatic disease might remain on chemotherapy for a long time, so don’t have the opportunity for their chemo brain to subside.


Patients who were in high functioning roles seem to notice the most impact, both in terms of their ability to perform the work itself and their ability to juggle the demands of work and family/social commitments.


“As for chemo brain, exercise helps with physical and therefore mental stamina”


Why does exercise help with chemo brain?

Exercise helps in so many ways to improve quality of life during and after chemotherapy, and, in fact, increases the likelihood of survival in many cancer types. As for chemo brain, it helps with physical and therefore mental stamina.


Loss of physical endurance, fitness and strength is also common with chemotherapy, and exercise reduces that loss. It helps create a better mood, reduces depression and anxiety, and aids sleep quality. All of these have an impact on cognition.


“Exercise increases blood flow to the brain and minimises the microscopic blood vessel damage that can occur with chemotherapy”


Exercise increases blood flow to the brain and minimises the microscopic blood vessel damage that can occur with chemotherapy. It also helps reverse the metabolic syndrome of high blood sugar/pre-diabetes and high cholesterol-related inflammation. We need to do more research into which of these components is the critical factor in the benefits of exercise, but it is likely to vary according to the individual patient.


What sort of exercise is best to help?

In short, any sort of exercise! To be more specific, it is best to get your heart rate up. International guidelines call for 150 minutes per week of moderate to vigorous intensity exercise for patients with cancer. While incidental exercise like walking to the shops is useful, it’s just not as beneficial as when you start to feel like you are working reasonably hard. That means breathing a bit faster, feeling the heart rate go up and breaking a sweat.


Cardiovascular exercise like walking, cycling, swimming; mind body exercise such as yoga and tai chi; and strength-based exercise such as resistance training are all good. Not every cancer patient will be able to participate at this level at all times, and it needs to be adapted according to ability during the chemo cycle as some days will require more rest. However, it will often be possible to do some exercise most days, especially with support from friends and family. A very valuable support is participating in an exercise physiology program tailored to cancer patients that is available at some cancer centres.


“Guidelines call for 150 minutes per week of moderate to vigorous intensity exercise for patients with cancer”


What other benefits does exercise have for people going through breast cancer treatment?

Exercise has so many benefits. Regular exercise reduces mortality from both cancer and other causes. It lifts the mood, improves sleep and translates into better functioning from day to day. It helps with tolerance of cancer treatments, meaning that the treatments are more likely to be completed, with greater chance of those treatments being beneficial.


Breast cancer treatments can weaken the bones, causing osteoporosis. Exercise like running, hopping, jumping and skipping helps reduce bone loss. It also often gets you out in the sunshine which can assist the bone-building effect of vitamin D and, of course, provides the social benefits of doing something with a friend.


For further information about breast cancer research, please visit



Breast Cancer Live Virtual Q&A – 30 September

Breast Cancer Trials will be hosting a virtual Q&A called Breast Cancer Trials: Let’s Talk About Sex on 30 September from 5-6:30pm AEST.

Breast Cancer Trials want to bring the discussion about the impact of breast cancer treatment and sex out of the shadows, offering all members of the general public a chance to ask any question about the subject/get advice about solutions during a free Q&A session featuring some of the country’s top experts. This is also an opportunity to learn about new research.

The experts featured are Professor Fran Boyle, Medical Oncologist Dr Belinda Kiely, breast cancer patient Rebecca Angus, and Professor Kate White, all of whom have studied or personally experienced the impact of breast cancer on a person’s sex life.

The session will be moderated by the TV presenter, commentator and author,  Annabel Crabb. 

To register your interest and ask a question to the panel of experts, go to




Dr Nick Zdenkowski, BMed FRACP PhD

Nick is a medical oncologist and a clinical researcher. He treats patients with a range of different types of cancer, and has a special interest in the care of patients with breast and gastro-intestinal cancer.



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