The (mis)classification of chemo-fog – methodological inconsistencies in the investigation of cognitive impairment after chemotherapy
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A growing number of studies report cognitive impairment after chemotherapy; indeed the phenomenon of chemo-fog is now almost universally accepted. We are concerned however that there is little if any consistency in the way in which patients are classified as showing cognitive impairment or not. We aim to demonstrate that different methods of analysis produce markedly different results, making the true extent of impairment unclear.
We analysed data from 92 breast cancer patients 4 weeks post-chemotherapy and from 42 healthy controls using 7 different methods, each taken from a different research paper in the area of cognitive impairment post-chemotherapy.
The extent of impairment was dependent on the method of analysis. Impairment ranged from 12 to 68.5% in the chemotherapy group and from 4.8 to 64.3% in the healthy control group.
This brief report highlights the contrasting degrees of cognitive impairment calculated by using legitimate statistical methods and demonstrates the need for a collaborative effort to standardise our methods that we might better understand the phenomenon of chemo-fog.
Keywordsbreast cancer chemotherapy cognitive impairment
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We thank the women who participated in the study, all hospital clinic and administrative staff and Roberta Morris for conducting many of the patient assessments. We also thank all of the consultants (Mr Allan, Mr Bishop, Dr Bloomfield, Dr Deutsch, Dr Hodson, Dr Mitra, Dr Sadler, Miss Shah, Dr Stein, Mr Whitehead, Mr Winstanley) and research nurses (Rose Errington, Jayne Hughes, Sonya Mash, Helen Mitchell, Elaine Noon, Victoria Rawlins, Frances Scott), for helping recruit patients to the study. Cancer Research UK funded the study, Dr Shilling and Dr Jenkins.
Conflict of Interest
The authors declare no conflict of interest. Dr Shilling had full access to all the data in the study and had final responsibility for the decision to submit for publication.
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