Cognitive functioning in thyroid cancer survivors: a systematic review and meta-analysis

BACKGROUND: Some thyroid cancer (TC) survivors experience cognitive symptoms.

PURPOSE: The purpose of this study is to perform a systematic literature review and meta-analysis comparing cognitive performance in TC survivors to controls.

METHODS: We performed a seven-database electronic search and hand-search. We performed duplicate independent reviews and data abstraction. Random effects meta-analyses reported standardized mean differences (SMDs) with 95% confidence intervals (CIs), where a negative value implies worse performance in the TC group.

RESULTS: We reviewed 1174 unique citations and 10 full-text papers. We included seven studies of 241 treated TC survivors and 273 controls. Cognitive function was statistically significantly worse in TC survivors in the following domains: Attention and Concentration (Digit Span Forwards) SMD - 0.37 (95% CI - 0.62, - 0.13, p = 0.003, four studies), Speed of Processing (Trail Making A) SMD - 0.36 (95% CI - 0.66, - 0.05, p = 0.022, four studies), and Language (Controlled Oral Word Association [COWAT]-Categories) SMD - 0.97 (95% - 1.31, - 0.64, p < 0.001, two studies). Executive Function results varied: COWAT-Letters SMD - 0.60 (95% CI - 0.94, - 0.27, p < 0.001, two studies), Digit Span Backwards SMD - 0.40 (95% CI - 0.64, - 0.15, p = 0.002, four studies), and Trail Making B test SMD - 0.20 (95% CI - 0.51, 0.10, p = 0.191, four studies). Statistical heterogeneity limited the COWAT-Categories and Digit Span Backwards meta-analyses.

CONCLUSIONS: Cognitive function was worse in TC survivors in multiple domains. Limitations included few studies, potential confounding, and lack of prospective data.

IMPLICATIONS FOR CANCER SURVIVORS: TC survivors may experience impairments in cognitive function and should report cognitive concerns to healthcare practitioners.