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Chemotherapy and Cognitive Function

The Mental Impairment Caused by Chemotherapy is Well Understood

Nov 12, 2009 David Olle

Many patients experience impaired cognitive function during and after cancer chemotherapy. Progress has been made in understanding and treating the condition.

The mental fogginess that patients often experience after receiving chemotherapy treatments is commonly called chemo brain. The phenomenon has been little studied and not well understood. Chemo brain was first recognized in breast cancer patients, but is now understood to occur in survivors of other cancers as well. The mechanisms by which chemotherapy could cause loss of cognitive function include vascular injury and oxidative damage, inflammation, direct injury to neurons, autoimmune responses, and anemia.

The Loss of Cognitive Function in Cancer Patients May be Due to Factors Other Than Chemotherapy

The cancer may cause direct effects on the central nervous system (brain and spinal cord). The cancer may cause indirect effects on the central nervous system due to systemic effects. Examples are organ failure, metabolic or electrolyte disturbances, and infection. Medications other than chemotherapy could cause loss of cognitive function. Examples include biologic response modifiers, such as interleukin and interferon, glucocorticoids, antidepressants and sedating agents.

A Study with Breast Cancer Patients

Breast carcinoma patients were divided into two groups:

a. Patients whose cancer had spread to the lymph nodes and were treated with adjuvant CMF (cyclophosphamine, methotrexate, and 5-fluoruracil). The patients also may or may not have received Tamoxifen. The patients must have been off chemotherapy at least six months prior to the start of the study.

b. A control group that had received the same surgical and radiological treatment, but no chemotherapy.

A battery of 14 neuropsychological tests covering a broad range of functions were performed on all patients. The patients were also interviewed with regard to cognitive problems they experienced in their daily lives, as well as psychological problems such as depression and anxiety.

The group receiving chemotherapy demonstrated extensive impairment of cognitive functions, including attention, mental flexibility, speed of information processing, visual memory, and motor and verbal functioning. Overall statistical analyses showed that 28% of the patients treated with chemotherapy were impaired in cognitive functioning, while 12% of the control group was impaired. There was no correlation between self-reported measures of cognitive impairment and test scores. The patient may have been experiencing anxiety or depression, and it is known that everyday experiences of cognitive functions can be different from cognition evaluated in neuropsychological tests.

Cognitive Function in Brain Tumor Patients

Patients with brain tumors, such as malignant glioma, suffer declines in cognitive function due to the effects of the cancer itself. The primary treatment for such patients is radiation, since many chemotherapeutic agents can not pass the blood-brain barrier. Treatment with a substance such as mannitol that opens the blood-brain barrier can permit the entry of chemotherapeutic agents into the brain. Neuwelt reported on such a study that improved survival of brain tumor patients with preservation of cognitive function. Meyers reported on the use of methylphenidate therapy on malignant glioma patients. Significant improvements in cognitive function and physical activities were observed.

Improved Understanding of Cognitive Decline Associated With Chemotherapy

In addition to chemotherapy, cognitive decline in cancer patients can be caused by complications from the cancer itself, as well as from other treatments. The effects are now better understood, and treatments are being developed that can reduce cognitive decline.

References:

National Cancer Institute. "Causes of Cognitive Disorders and Delirium." www.cancer.gov

Meyers C. "Methylphenidate Therapy Improves Cognition, Mood, and Function of Brain Tumor Patients." J Clin Oncology. 1998; 16:2522-2527.

Neuwelt E. "Primary CNS Lymphoma Treated With Osmotic Blood-brain Barrier Disruption: Prolonged Survival and Preservation of Cognitive Function." J Clin Oncology. 1991; 9:1580-1590.

Schagen S. "Cognitive Deficits After Postoperative Adjuvant Chemotherapy for Breast Cancer." Cancer. 1999; 85:640-650.

The copyright of the article Chemotherapy and Cognitive Function in General Medicine is owned by David Olle. Permission to republish Chemotherapy and Cognitive Function in print or online must be granted by the author in writing.

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