Editor’s note: One in a series of articles on managing cancer-related symptoms from the Oncology Nursing Society.

Basic cognitive abilities are measured by attention and concentration, executive function, information processing speed, language, visuospatial skills, psychomotor ability, learning, and memory (Jansen, Miaskowski, Dodd, Dowling, & Kramer, 2005). Cognitive impairment, then, is defined by Allen (2011) as a decline in function of one or many of these domains. Unfortunately, many cancer diagnoses or their treatments can lead to cognitive impairment for patients—a distressing side effect and one that may continue to afflict patients after treatment has ended.

The incidence of cognitive impairment varies by type of cancer, type of treatment, and time since diagnosis (Allen, 2011). Early studies on cognitive impairment focused on patients with brain tumors and, interestingly, found that 50% to 80% of these patients have cognitive impairment at the time of diagnosis (Tucha, Smely, Preier, & Lange, 2000). This suggested that the impairment was mainly caused by the tumor itself. More recent studies have concluded that cognitive impairment is present in other populations of patients with cancer prior to treatment: 11% to 35% of patients with breast cancer, 70% to 80% of patients with lung cancer, and 40% of patients with acute myeloid leukemia (Ahles et al., 2007; Hermelink et al., 2007; Hurria et al., 2006; Meyers, Albitar, & Este, 2005; Meyers, Byrne, & Komaki, 1995). And, as mentioned earlier, additional research has found that 20% to 30% of cancer survivors experience significant cognitive impairment after treatment has ended (Vardy, Wefel, Ahles, Tannock, & Schagen, 2007; Von Ah et al., 2009). Survivors experiencing this symptom often report subtle declines in memory, concentration, and executive functioning (Allen, 2011), which may lead to difficulties at home and work.

Because of the amount of interaction oncology nurses have with their patients, they are in a unique position to recognize cognitive changes in those patients. Surveys and clinician-administered tests are available (see Subjective instruments used to measure cognitive impairment), but many require special training to administer. A detailed assessment of patient self-reports of problems, such as forgetfulness, difficulty with memory, and difficulty with multitasking, can be helpful in determining potentially treatable causes and to determine if symptoms are worsening over time (Allen, 2011). If so, oncology nurses should refer patients to a neuropsychologist for additional evaluation (Allen, 2011).

Putting Evidence Into Practice

To promote nursing practice that is based on evidence, the Oncology Nursing Society (ONS) launched the Putting Evidence Into Practice (PEP) program in 2005. ONS PEP teams consisting of advanced practice nurses, staff nurses, and a nurse scientist were charged with reviewing the literature to determine what treatments and interventions are proven to alleviate many cancer-related problems that are sensitive to nursing interventions. Each team classified interventions under the following categories: recommended for practice, likely to be effective, benefits balanced with harms, effectiveness not established, effectiveness unlikely, not recommended for practice, and expert opinion.

However, to date, there are no evidence-based preventive measures for cognitive impairment caused by cancer or cancer treatment. Possible interventions are classified as effectiveness not established and will be identified here.

Effectiveness not established

These items have insufficient or conflicting data or data of inadequate quality with no clear indication of harm.

Medications

Methylphenidate is a psychostimulant that was found to improve cognitive function in adults with cancer in studies by Bruera, Miller, Macmillan, and Kuehn (1992), Gagnon, Low, and Schreier (2005), and Meyers, Weitzner, Valentine, and Levin (1998). However, three more recent randomized, controlled trials failed to demonstrate significant improvement in cognitive functioning in patients who were given methylphenidate (Butler et al., 2007; Lower et al., 2009; Mar Fan et al., 2008). Additional research is needed.

Studies also have been conducted with donepezil and modafinil with similar mixed results. Of the two trials conducted with donepezil, Shaw et al. (2006) reported some improvement in cognitive functioning; however, simultaneous improvements in tumor size may have confounded the results. The second trial (Jatoi et al., 2005) failed to find a significant effect of donepezil and vitamin E on cognitive function. With modafinil, all three studies (Blackwell, Petroni, Shu, Baum, & Farace, 2009; Kohli et al., 2009; Lundorff, Jonsson, & Sjøgren, 2009) reported improvement in some aspects of cognitive performance, but differed on which aspects. Additional randomized, controlled trials are needed to determine efficacy (Allen et al., 2011).

Complementary and alternative therapies

The impact of exercise on cognitive impairment was studied in two nonrandomized trials. Schwartz, Thompson, and Masood (2002) combined four months of exercise with the administration of methylphenidate and recorded improvements in visual attention, motor speed, and cognitive flexibility. Korstjens, Mesters, van der Peet, Gijsen, and van den Borne (2006) noted improvements in cognitive function after 3 months of an exercise program coupled with an educational program on fatigue. However, cognitive function was measured by self-report with no objective measurements used. Further replication with comparison groups and objective measures is needed for this promising intervention (Allen et al., 2011).

Vitamin E received mixed results from two separate trials. Chan, Cheung, Law, and Chan (2004) administered 1,000 international units of vitamin E twice daily for 1 year and recorded improvements in global cognition, verbal and visual memory, and executive function. However, Jatoi et al. (2005) failed to find a significant effect when patients were given 5 mg per day of donepezil and 1,000 international units per day of vitamin E for 3 months. Differences in study design and time of these two studies was noteworthy (Allen et al., 2011).

Cognitive training program interventions

Several studies explored the use of cognitive training programs to improve cognitive impairment in patients with cancer. These programs varied in design, personnel, involvement with caregivers, and duration (Allen et al., 2011), and consisted of computer-based programs (Ferguson et al., 2007; Gehring et al., 2009; Poppelreuter, Weis, & Bartsch, 2009) or sessions with trained healthcare professionals (Locke et al., 2008; McDougall, 2001; Sherer, Meyers, & Bergloff, 1997). All of the programs offered concurrent psychoeducational training. And, while all appeared to have positive results, many of the studies were limited by small sample sizes and a lack of a comparison group (Allen et al., 2011).

Areas for research

Allen et al. (2011) determined focused areas of needed research to address cognitive impairment in patients with cancer. Researchers should aim to understand the prevalence and trajectory of cognitive impairment across various types of cancers and their treatments and identify potential predictors of cognitive impairments so that patients at risk may be treated sooner. In addition, assessment tools that are reliable, valid, sensitive to subtle changes, and easily conducted in a clinical setting are needed. Research should strive to identify the underlying physiologic mechanism associated with cognitive impairment and to identify symptoms of cognitive impairment (e.g., pain, sleep disturbance, fatigue, depression) that may hinder effective treatment. Together, results from these research items may lead to effective evidence-based interventions to treat patients suffering from cognitive impairment.

Sean Pieszak is a staff editor in the Publications department at the Oncology Nursing Society (ONS) in Pittsburgh, Pennsylvania. More information about the ONS Putting Evidence into Practice classification for cognitive impairment can be found at http://www.ons.org/Research/PEP/cognitive.

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