Cognitive function in postmenopausal breast cancer patients one year after completing adjuvant endocrine therapy with letrozole and/or tamoxifen in the BIG 1-98 trial

Abstract

Endocrine therapy for breast cancer may affect cognition. The purpose of this study was to examine whether cognitive function improves after cessation of adjuvant endocrine therapy. Change in cognitive function was assessed in 100 postmenopausal breast cancer patients in the BIG 1-98 trial, who were randomized to receive 5 years of adjuvant tamoxifen or letrozole alone or in sequence. Cognitive function was evaluated by computerized tests during the fifth year of trial treatment (Y5) and 1 year after treatment completion (Y6). Cognitive test scores were standardized according to age-specific norms and the change assessed using the Wilcoxon signed-rank test. There was significant improvement in the composite cognitive function score from Y5 to Y6 (median of change = 0.22, effect size = 0.53, P < 0.0001). This improvement was consistent in women taking either tamoxifen or letrozole at Y5 (P = 0.0006 and P = 0.0002, respectively). For postmenopausal patients who received either adjuvant letrozole or tamoxifen alone or in sequence, cognitive function improved after cessation of treatment.

Fig. 1

CONSORT diagram of the BIG 1-98 Cognitive Function Substudy. T tamoxifen for 5 years, L letrozole for 5 years, T → L tamoxifen for 2 years followed by letrozole for three years, L → T letrozole for 2 years followed by tamoxifen for 3 years, ET endocrine therapy, Y5 cognitive function assessment taken at the end of 5 years of ET, Y6 cognitive function assessment taken approximately 1 year after completion of ET

Fig. 2

Change in median age-adjusted composite score from the assessment taken at the end of endocrine therapy (Y5) to the assessment taken approximately 1 year after completion of endocrine therapy (Y6) according to endocrine therapy received, showing significant improvement in cognition, as measured by the composite score, from Y5 to Y6