Patients treated for cancer frequently complain of cognitive dysfunction. They evoke a chemobrain (or chemofog) which, although generally mild, has a negative impact on their quality of life. Unfortunately, even today their cognitive disorders are often ignored by doctors, even in the event of a complaint expressed by the patient. Therefore, they are underdiagnosed and poorly taken care of. However, since the 1990s, research on this issue has increased considerably and confirms the need to take these disorders into account. Some studies, for example, report difficulties in returning to professional activity among women treated for breast cancer because of cognitive disorders resulting from the disease. There are also some patients who report having to put in place compensation strategies to successfully carry on their social and professional life following their cancer. Thus, today there are cancer centers in France that offer neuropsychological consultations in order to investigate the patient’s cognitive complaint and to offer care or follow-up adapted to each patient.
Our article aims to present a brief summary of cognitive disorders in cancer and their causes before exploring ways to detect them and finally to develop possible treatments for these disorders.
What cognitive functions are affected by cancer and its treatment?
To this day, neuropsychological studies have highlighted several cognitive functions that would be affected by cancer and its treatments.
First, studies have found the following effects: impaired attention, with complaints of great distractibility from patients, difficulty concentrating, or even focusing on a task. Then, impairment of working memory, a cognitive function that allows information to be stored and temporarily manipulated in order to perform a task. Studies also identified difficulties in episodic memory with problems expressed by patients remembering recent events. One can also find a slowdown in the processing speed of information in memory. Finally, studies have highlighted impairment of executive functions which leads to difficulties in planning, inhibition or even mental flexibility.
Nevertheless, it is important to note that there is a great variability in the studies, with a variation ranging from 16% to 75% of patients presenting significant cognitive deficits compared to their previous cognitive level. However, studies on the subjective cognitive complaint of patients show more homogeneous and higher scores, up to 90% of patients expressing a cognitive complaint that impacts their daily life. It is therefore necessary to take this aspect of cancer management into account.
Why and how to evaluate cognitive difficulties linked to cancer disease and treatment ?
Reasons for evaluating cognitive difficulties associated with cancer are multiple. The first one is to better specify the subjective cognitive complaint of the patient and eventually his close relations. More than that, it is important to objectify disorders. This allows a recognition of the difficulties of the patients that can relieve them. In fact, knowing what are the damaged or preserved abilities can help to propose an adapted care or treatment. Thus, evaluating cognitive difficulties could improve the quality of life of the patient, during and/or after the treatment of the cancer.
In order to draw the cognitive profile of the patients, a neuropsychological assessment is mandatory. The appointment lasts approximately 1.30 to 2 hours and is composed of three steps. The first one is the interview. During this part of the appointment, the psychologist collects information on the patient, their studies and career history, family situation, their disease and how the cognitive disorders started, their impact on their quality of life, their psychological and emotional state, awareness about personal difficulties, how they adapt to face the disorder etc. Some questionnaires have been developed and validated for patients with cancer to allow them to express difficulties they have in regards to their cognitive disorders. For example, the questionnaire Fact-Cog includes items about memory, attention, focusing, language and reasoning, taking functional implications, difficulties observed by the entourage, changes in cognitive functions appearing with time and their impact on the patients’ quality of life into account.
The second part of the appointment revolves around the neuropsychological evaluation of the patient’s cognitive functions. The International Cognition and Cancer Task Force (ICCTF) recommends the use of certain tests with the aim to compare the different evaluations of people who present a cancer, between them, and between the several evaluations. For example, they recommend using the Hopkins Verbal Learning Test-Revised (HVLT-R) (Brandt & Benedict, 2001) in order to evaluate the episodic memory. For the processing speed and the executive functions, they chose the Trail Making Test (part A and B) (Lezak, 1976). There is the Controlled Oral Word Association Test (COWAT) (Benton, 1983) to evaluate the verbal fluency and the Paced Auditory Serial Addition Test (PASAT) (Gronwall, 1977) for working memory and attention. The first three tests presented have in common some adapted psychometric properties (particularly sensibility and standardization), parallel forms and they are translated in several languages.
The last part of the appointment is generally an oral report of the preserved and damaged cognitive functions of the patient, and some propositions of treatment that could be realized in the next weeks and months.
What are the treatments ?
Different treatments proposals can be made to the patient depending on the stage or time of the complaint. The objective is to improve their quality of life and promote their social and professional reintegration.
Very often, psycho-education is offered to patients, providing explanations of the cognitive functions affected and advice according to the person’s difficulties (attention, memory, etc.). In addition to that, it is important to suggest the implementation of a psychological follow-up, especially when the patient presents one or more factors that can impact cognitive functions (e.g. mood disorder) and consequently the potential benefits of the treatment. In parallel with a psychological follow-up, various interventional treatments can be proposed by members of the multidisciplinary team (occupational therapist, speech therapist, psychologist). Indeed, in these treatments, there are pharmacological interventions, physical exercise interventions.
From the side of drug treatment, only a few molecules show a little bit of interest in the reduction of cognitive disorders. Psychostimulants like methylphenidate are used in order to treat cognitive diseases in children with cancer. The data concerning effects on adults are controversial. A lot of substances were tested like memantine, ginkgo biloba, erythropoietin (EPO) but didn’t show any positive effect on damaged cognitive functions. Other substances from the field of neuroprotection and neurocognition are studied for prevention of post-radiotherapy effects like lithium, pioglitazone or ramipril. For the prevention of post-chemotherapy effects, the fluoxetine, ibuprofen and nicotine patch are tested.
Then, we know that without drugs physical exercise shows significant results concerning the improvement of cognitive functions in healthy people, particularly on executive functioning. Some studies have attempted to observe the same effects in people suffering from cancer by introducing physical exercises like yoga, tai-chi, reinforcement or walk. Positive results were observed in the study of Hartman et al. on the processing speed. This study included about 150 minutes of physical activity a week during 12 weeks. The participants were supported by advice, a connected support to follow their activities and a regular exchange through emails. Results were positive particularly for patients who received their diagnosis less than two years ago so it seems important to begin this type of “treatment” as soon as possible after the announcement of the diagnosis. Then, cognitive exercises have also been tested to stabilize or to improve cognitive functioning in patients with cancer. Some animal datas suggested that these exercises added to the physical ones would be more efficient than practiced one by one.
There are also specific behavioral interventions, including meditation or acupuncture, which mainly have an effect on subjective aspects and fatigue. However, behavioral interventions focusing on cognition are the ones most often proposed. They are mainly based on cognitive remediation which consists on “restoring better quality cognitive functioning, thus allowing the people who benefit from it to have increased capacities to manage their daily and social life” (Passerieux, 2010). Thus, adaptive strategies (e.g., arranging the environment, compensations, etc.) would be proposed to the patient according to their preserved abilities and functions. The results of this type of treatment show an improvement in verbal episodic memory after 2 months of treatment, but also an improvement in attention. There was a reduction in subjective cognitive complaints, better social functioning and a better quality of life.
In view of these elements, the management of cognitive functions in people affected by cancer is a crucial element for the improvement of their quality of life. It is important to continue to develop these interventions. Some studies propose to promote work on metacognition (i.e. knowledge of one’s own abilities, strengths, weaknesses, and cognitive functioning) within these interventions and specify the importance of taking into account potential factors associated with cognitive disorders (such as fatigue, sleep disorders, and mood disorders) that can impact the result of treatments.
Conclusion
To conclude, the cognitive disorders linked to cancer are multiple. It is necessary to continue to evaluate them precisely in order to offer optimal care for the patients. It can be composed of pharmacological treatments and non-pharmacological interventions like physical exercises or behavioral interventions.
Words we have learned :
- Chemobrain (or chemofog) : Brouillard cognitif
- Underdiagnosed : Sous-diagnostiqué
- To treat : Traiter
- The damaged or preserved abilities : Les habiletés endommagées et préservées
- Conseil : Advice
- Arranging the environment : Aménager l’environnement
- Daily life = Vie quotidienne
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