When patients and physicians talk about “chemobrain,” the standard understanding of the problem is that it is a result of chemotherapy because it is usually noticed after chemotherapy begins.18 What the Phillips trial has done is suggest that chemotherapy may not be fully responsible for cognitive deficits. The results from this trial highlight the importance of using a radiotherapy comparison group, as those patients receiving radiotherapy also demonstrated similar decline in cognitive performance tasks.

What the cause or causes of this cognitive impairment is/are is a matter subject to debate. Eschewing treatment side-effects as the definitive reason for the impairment, the changes could be associated with the stress, anxiety, and mood changes associated with the diagnosis of the cancer.19 They may also be a result of altered brain structure and function due to the cancer.12–15   

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These findings also have significant clinical implications. Clinicians should discuss the possibility of the long-term cognitive effects of both chemotherapy and radiotherapy with their patients. Although cognitive deficits may last for years, they are domain specific and not global. Patients that report that cognitive deficits interfere with their ability to perform daily tasks should be further evaluated, and referred to a neuropsychologist to rule out other causes and be considered for other strategies to compensate for any deficits.17,20


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