Your brain after cancer: what to expect and how to help

Article written by Bryan Neth, MD, Ph.D. and Eva Alden, PhD, LP

If you’ve ever felt like your brain isn’t working the way it used to during or after cancer treatment, you’re not imagining it. You may find yourself forgetting simple things, like where you placed your keys or what you were about to say. You might struggle to concentrate on a task or feel mentally slower than you did before your diagnosis. This experience is often called chemo brain.

What is it and why does it happen?

Historically, chemo brain and “brain fog” was described in patients with breast cancer undergoing cancer treatment. We now know that thinking and memory changes are common in people diagnosed with many types of cancer and occur in up 75% of patients at some point in their cancer journey. You may also hear the term cancer-related cognitive impairment (or CRCI), which some doctors and researchers refer to when discussing the thinking changes in cancer survivors. While the name suggests it’s caused only by chemotherapy, that’s not always the case. Other treatments like hormone therapy, radiation, surgery, and immunotherapy can affect how clearly a person thinks, remembers, and focuses. Thinking changes can also be seen prior to the start of cancer treatment which is likely due to the whole-body effects of the cancer itself. What’s important to know is that these changes in brain function are real, they’re common, and they don’t mean you’re doing anything wrong.

People often describe chemo brain as feeling foggy or slow. You might lose your train of thought in the middle of a conversation or take longer to finish routine tasks. For some, this fog lifts quickly after treatment ends. For others, it may come and go or last long after treatment. Either way, it can feel frustrating especially when it interferes with work, relationships and family life, or daily activities.

We don’t fully understand why chemo brain happens, but it’s likely the result of several things. Treatments can negatively affect healthy brain cells even if the cancer is not in the brain, and inflammation caused by cancer or its treatment may also play a role. Common symptoms faced by patients with cancer, including fatigue, sleep problems, pain, stress, anxiety, and depression can also worsen thinking changes. It’s not always possible to point to a single cause, which can make it harder to explain, but knowing that the experience is real and shared by many others is an important first step toward getting help.

What can help?

I want you to know there are ways to feel more in control. There’s no quick fix, but even small changes can have an impact. One of the most helpful tools is movement. I tell my patients physical activity is 1, 2, and 3 for brain health and has benefit for chemo brain. Even a short daily walk can improve blood flow to the brain, boost your mood, and reduce fatigue. Sleep is just as important. Poor rest can make brain fog worse, so try to keep a regular sleep schedule. If sleep is hard, talk with your healthcare team. Staying organized can also ease the mental load. Write things down, set reminders, and stick to simple routines. These tools are ways to work with your brain as it heals. Focusing on one task at a time, in a quiet space, may also help your brain do its best work. Diet matters too. Eating more fruits, vegetables, quality protein, and healthy fats likely olive oil can support clearer thinking over time. And don’t forget to exercise your mind. Reading, puzzles, or learning something new. I tell patients to find something that they enjoy but also challenges their thinking.

Find support

It’s also important to talk about what you're going through. Chemo brain can feel isolating, especially if the people around you don’t understand what it is. Letting friends, family, or co-workers know about your experience can help set expectations and give them the chance to support you better. If thinking issues are interfering with your ability to work or care for yourself, talk to your healthcare team. There may be other reasons for your symptoms, such as medication side effects, vitamin deficiencies, or thyroid issues. Your doctor may recommend working with a cognitive specialist, occupational therapist, or counselor who can help you find strategies to improve function and rebuild confidence.

What I often remind my patients of is that you’re not alone. Chemo brain can be frustrating, but it doesn’t define you. Some days will feel easier than others, and progress may come in small steps. That’s expected. With support, many people begin to feel clearer and more like themselves again. And while the path may not always be easy, you don’t have to walk alone.

HELPFUL LINKS:

• Mayo Clinic – Chemo brain
• American Cancer Society – Changes in memory, thinking, and focus (chemo brain)
• NCCN – Survivorship care for cancer-related late and long-term effects
• Connect with others in the Cancer: Managing symptoms discussion group