The objective of this study was to examine the associations between aromatase inhibitors (AIs) and side effects less frequently reported in the literature, including difficulty concentrating, forgetfulness, hair loss, and numbness in the extremities.

Data were analyzed from a cohort of 146 breast cancer patients initiating AI therapy and followed for 1 year and a cohort of 144 postmenopausal women without a history of cancer followed for 6 months. At baseline (prior to AI therapy for breast cancer patients), and at 3 months, 6 months, and 1 year (for breast cancer patients only), a comprehensive questionnaire was administered that ascertained data on symptoms. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated using logistic regression for new onset of symptoms among the breast cancer patients compared to the women without a history of cancer.

Among the breast cancer patients, 34.2% were treated with chemotherapy prior to AI treatment. Over the first 6 months of AI treatment, breast cancer patients had significantly higher odds of reporting new onset of forgetfulness (OR 4.00; 95% CI 1.67, 9.59), difficulty concentrating (OR 2.73; 95% CI 1.29; 5.78), hair loss (OR 4.12; 95% CI 1.86, 9.17), and numbness/tingling in the extremities (OR 2.47; 95% CI 1.09, 5.62) compared to women without a history of cancer. Similar increases in odds were observed for the subgroup of women not treated with chemotherapy versus the comparison group.

AI-related symptoms should be monitored and addressed so that adherence to therapy is maintained.