Side Effects - Cognitive Dysfunction

Cognitive dysfunction (also known as chemo brain or brain fog)


  • Cognitive impairment is commonly observed in patients with cancer and those in remission (1, 2 3)       
  • Cognitive impairment is a common complaint among cancer survivors and may be a consequence of the tumors themselves or direct effects of cancer-related treatment (e.g., chemotherapy, endocrine therapy, radiation)
  • Studies have shown MRI changes in those with complaints of brain fog / chemo brain
  • For some survivors, symptoms persist over the long term and, when more severe, can impact quality of life and function (4)
  • Cognitive dysfunction is most commonly connected with chemotherapy (sometimes referred to as “chemobrain”), but evidence suggests that therapies other than chemotherapy, such as endocrine therapy and radiation, may be associated with cognitive impairments
    • 40% increase of the likelihood of self-reported memory problems (5) 
    • Growing evidence supports the patient experience of cognitive dysfunction associated with cancer and its treatment (6)


  • Memory loss
  • Trouble paying attention; making decisions
  • Difficulty with activities of daily living
  • Make silly mistakes; difficulty writing
  • Trouble making decisions

National Comprehensive Cancer Network (NCCN) Principles for cognitive dysfunction (6)

1.    Growing evidence supports the validity of patient-reported experience of cognitive dysfunction associated with cancer treatment:  there is modest correlation between patient reports of cognitive dysfunction and objective deficits with testing
2.    There is limited evidence to guide management of this conditions, especially for cancers other than breast
3.    Patients benefit from validation of their symptom experience; a thorough evaluation of this concerns and related issues and education
4.    Imaging studies are generally not helpful, except when indicated by high-risk illness or focal neurologic deficits
5.    Patients who present with symptoms of cognitive impairment should be screened for potentially reversible factors that may contribute to cognitive impairment, especially depression
6.    Patients exposed to treatment known to cause cognitive dysfunction (i.e., chemotherapy, brain irritation) are likely to experience this condition.
7.    Currently, no effective brief screening tool for cancer-associated cognitive dysfunction has been identified.  The mini-mental state examination (MMSE) and similar screening tools lack adequate sensitivity for subtle decline in cognitive performance

According to NACES survivor (who wished to remain anonymous):  

Anonymous AI/AN Cancer Survivor"This brain fog lasted 3 years, then suddenly it was like watching fog, no longer was covering my eyes and my brain, but slowly rose and dissipated into the sky"

  1.  Wefel JS, Vardy J, Ahles T, Schagen SB. International Cognition and Cancer Task Force recommendations to harmonise studies of cognitive function in patients with cancer. Lancet Oncol. 2011;12(7):703-708. doi:10.1016/S1470-2045(10)70294-1
  2.  Pendergrass JC, Targum SD, Harrison JE. Cognitive Impairment Associated with Cancer: A Brief Review. Innov Clin Neurosci. 2018 Feb 1;15(1-2):36-44. PMID: 29497579; PMCID: PMC5819720.
  3.  Jean-Pierre P, Winters P, Ahles T, et al. Prevalence of self-reported memory problems in adult cancer survivors: a national cross-sectional study. J Oncol Pract. 2012;8:30–34.
  4.  Denlinger CS, Ligibel JA, Are M, Baker KS, Demark-Wahnefried W, Friedman DL, Goldman M, Jones L, King A, Ku GH, Kvale E, Langbaum TS, Leonardi-Warren K, McCabe MS, Melisko M, Montoya JG, Mooney K, Morgan MA, Moslehi JJ, O'Connor T, Overholser L, Paskett ED, Raza M, Syrjala KL, Urba SG, Wakabayashi MT, Zee P, McMillian NR, Freedman-Cass DA; National Comprehensive Cancer Network. Survivorship: cognitive function, version 1.2014. J Natl Compr Canc Netw. 2014 Jul;12(7):976-86. doi: 10.6004/jnccn.2014.0094. PMID: 24994918; PMCID: PMC4465252.
  5.  Jean-Pierre P, Winters PC, Ahles TA, et al. Prevalence of self-reported memory problems in adult cancer survivors: a national cross-sectional study. J Oncol Pract. 2012;8:30–34.
  6.  NCCN