Comparison with Baseline Performances

The second aim of the current study was to monitor the cognitive function of a sample of adult CML patients over a twelve month period. Participants’ performances on measures of attention and working memory, motor and processing speed, and executive function, completed six and twelve months after commencing imatinib treatment, were compared to baseline performances. Participants’ completed the baseline assessment in the days or weeks following diagnosis, and prior to starting imatinib therapy.

There was no significant decline in any area of attention and working memory, motor and processing speed, or executive function. This is consistent with the samples self- report, as no patient described any concerns about their cognition at the six or twelve month review. Furthermore, the lack of decline is concordant with findings described by Pedersen et al. (2009) in his study of the long-term cognitive effects of chemotherapy in testicular cancer but contradicted previous longitudinal oncology research that identified subtle but enduring deficits in attention, processing speed, and executive function (Schagen et al., 2006; Scherwath et al., 2006; Wefel et al., 2004). However, much of this research focused on cognition in breast cancer patients treated with different chemotherapy agents. Pedersen et al. (2009) argued that findings from these earlier studies might not be generalisable to different cancer groups and treatments. Furthermore, many chemotherapy treatments are not highly specific and risk damage to otherwise healthy tissue (Wefel et al., 2008). Therefore, patients receiving traditional chemotherapy agents might experience greater adverse consequences than patients receiving highly targeted molecular therapies such as imatinib. Given the difference between these medications, there is no human comparison for the current research findings and as such the results of the present study act as an important baseline for ongoing research in this domain to clarify these issues further. In this next section, the trends in the data will be discussed in more detail. Attention and Working Memory

Digit Span Subtest (WAIS-III)

A comparison of the central trends in the data indicated that there was no significant change in participants’ performance on the Digit Span subtest by the six or twelve 83

month review. Often improvement is expected as a result of repeated exposure to the same material, however practice effects for this measure are reported to be negligible (McCaffrey, Duff & Westervelt, 2000).

Motor and Processing Speed

Digit Symbol Coding Subtest (WAIS-III)

There was no significant decline on this measure of processing and motor speed. In fact, the analysis of group trends revealed a non-significant tendency towards improvement on the Digit Symbol Coding subtest by the twelve month assessment. Whilst a lack of improvement with repeated exposure to the same measure can be clinically meaningful, this is not the case with the Digit Symbol Coding subtest, as only modest practice effects would be expected across serial assessments (Lezak et al., 2004; McCaffrey et al., 2000). These results contradict Grove at al.’s (2003) findings which indicate that the inhibition of protein kinase leads to impaired synaptic efficiency. However as mentioned previously, it is difficult to generalise these findings to humans as imatinib was injected directly into the CNS of these animals, and therefore would be expected to have greater adverse effects.

Executive Function

Verbal Fluency Subtest (Letter and Category Fluency Conditions) (D-KEFS)

A review of the central trends within the data revealed no significant change in the letter fluency condition of the Verbal Fluency subtest by the twelve month assessment. Levine, Miller, Becker, Selnes and Cohen (2004) and others (Dikmen, Heaton, Grant, & Temkin, 1999) indicated that whilst some improvement in verbal fluency is expected with practice, the magnitude of this difference is often small (3.08 increase in raw score) and therefore potentially non-significant.

Trails B (Trail-making Test)

The repeated measures ANOVA revealed no significant change in the samples performance on the Trails B component of the Trail-making test over time. The literature about the benefits of practice on the Trails B component of the Trail-making test is inconsistent (Basso, Bornstein, & Lang, 1999; Bornstein, Baker, & Douglas, 1987; Durvasuka et al., 1996); therefore it is again difficult to establish whether the lack of improvement is of clinical importance.

Sorting Test (D-KEFS)

The repeated measures ANOVA revealed a non-significant trend towards improved performance on the free sort condition of the Sorting Test at the twelve month review. The absence of significant change across assessments is curious as Dikmen et al. (1999) indicated that tests involving problem solving and strategy, such as the Sorting Test, tend to have the largest practice effects. This is likely to be associated with the notion of test-wiseness mentioned above; as participants become familiar with the task, they refine and more readily employ strategies for successful problem solving (Lezak et al., 2004).

Findings from the Sorting Test should be interpreted with some caution, as the psychometric qualities of a number of measures in the D-KEFS have been criticised. Schmidt (2003) claimed that the reliability values in the D-KEFS were generally below the minimum accepted standard, and could not be recommended for clinical use. Whilst Shunk, Davis, and Dean (2006) also raised concerns about the measures’ psychometric properties but indicated that the test’s strength was associated with its ability to provide rich qualitative information. In contrast, Homack, Lee, and Riccio (2005) described the D-KEFS as a promising clinical and research tool. Further to this, early research undertaken by De Renzi Faglioni, Savoiardo and Vignolo, 1966 and others (McFie & Piercy, 1952; Newcombe, 1969) on the use of card sort tests (as cited in Lezak et al., 2004) claimed that the test was insensitive, as it failed to differentiate healthy individuals from brain injured patients.

In summary, the pattern was one of stable cognitive function over time, with some areas of non-significant improvement in processing speed and executive function.