Furthermore, the study demonstrated that attention/working memory, verbal learning/memory, and complex processing speed were most affected in patients with cancer vs healthy controls, but there was no association between overall cognitive function and fatigue, quality of life, anxiety/depression, or any blood test.

In regard to chemotherapy recipients, 32% of patients had cognitive symptoms at 6 months compared with 16% of those who did not receive chemotherapy (P = .007), but there was no significant difference between the 2 groups at 12 months (29% vs 21%, respectively; P = .19).

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Dr. Vardy told Cancer Therapy Advisor that the lack of significant difference in the rates of cognitive impairment between those who did and did not receive chemotherapy suggest that cancer, rather than chemotherapy, was the main cause of the impairment. However, the researchers did not identify the underlying cause of the cognitive impairment despite extensive biological correlative studies.

“Our results suggest that health professionals should be advising colorectal cancer patients that they may notice difficulties with their memory and concentration, and that for some this may not improve within the first year or two,” Dr. Vardy noted. “The reassuring finding from our study is that those who received adjuvant chemotherapy did not consistently have worse cognitive impairment than those who did not require chemotherapy.”

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“At present we do not know how best to treat this impairment but 

health professionals need to consider how best to present information to cancer patients that may have memory difficulties,” Dr. Vardy concluded.


  1. Vardy JL, Dhillon HM, Pond GR, et al. Cognitive function in patients with colorectal cancer who do and do not receive chemotherapy: a prospective, longitudinal, controlled study [published online ahead of print on November 2, 2015]. J Clin Oncol. doi: 10.1200/JCO.2015.63.0905.