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Blood, 15 November 2004, Vol. 104, No. 10, pp. 3003-3004.
Cognitive side effects of myeloablative allogeneic hematopoietic cell transplantationDARTMOUTH MEDICAL SCHOOL
The longitudinal, neuropsychological assessment study reported by Syrjala and colleagues suggests that long-term cognitive side effects of myeloablative allogeneic hematopoietic cell transplantation may not be as common as previous research has suggested.
The results of the study demonstrated a significant reduction in performance on all tests of cognitive functioning at the 80-day posttransplantation assessment; however, performance returned to pretransplantation levels at the 1-year assessment on all measures except for grip strength and motor dexterity. Interestingly, a higher percentage of patients than expected scored below published norms prior to transplantation, and performance on tests of verbal fluency and memory were below norms at all 3 testing points. This pattern of results illustrates the critical importance of longitudinal studies. Previous studies that have assessed patients only after treatment have interpreted similar percentages of below normative performance as an indication of the impact of the cancer treatment under study; whereas Syrjala et al were able to demonstrate that similar levels of impairment were, in fact, present before treatment.
Improvement in methodology does not necessarily eliminate all ambiguity from the interpretation of the results, as the authors recognize. From a patient's point of view, the most positive interpretation would be that HCT causes short-term cognitive changes but not long-term cognitive deficits. However, as the authors discuss, the pretreatment performance on the neuropsychological tests may have been lowered due to psychological distress, medical illness, or medications that could have had sedating or other effects on the central nervous system, and may not have represented a "true" measure of cognitive capabilities. In this scenario, one might have predicted that to conclude that HCT had no adverse effects on cognitive functioning would require 1-year test scores above pretreatment levels. An alternative hypothesis is that only a subgroup, perhaps the minority, of patients is vulnerable to long-term cognitive problems secondary to cancer treatments.2 Therefore, examining groups of patients may mask a pattern of results suggesting that most patients recover to normal levels of cognitive functioning after treatment, whereas a subgroup of patients continues to experience deficits. Data from their study provide some support for this hypothesis: patients who had not received chemotherapy, other than hydroxyurea, prior to HCT and patients not receiving chronic graft-versus-host disease medications at 1 year were at lower risk for cognitive impairment at the 1-year assessment. Genetic, hormonal, and immunologic factors may also be important in determining vulnerability to cognitive changes associated with cancer treatments.3 The study reported by Syrjala and colleagues represents a significant advancement in understanding cognitive changes associated with HCT and is a model for future research in this area. References
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| Copyright © 2004 by American Society of Hematology Online ISSN: 1528-0020 | |||||||||||
