Prospective evaluation of finger two-point discrimination and carpal tunnel syndrome among women with breast cancer receiving adjuvant aromatase inhibitor therapy Abstract Purpose Aromatase inhibitors (AIs) are associated with musculoskeletal symptoms and risk of developing carpal tunnel syndrome (CTS), which can impair quality of life and prompt treatment discontinuation. The incidence of CTS and clinical utility of diagnostic tests such as 2-point discrimination (2-PD) have not been prospectively examined among women receiving AIs. Methods Postmenopausal women with stage 0-III hormone receptor-positive breast cancer who were enrolled in a randomized clinical trial investigating adjuvant AIs (Exemestane and Letrozole Pharmacogenetics, ELPh) underwent prospective evaluation of 2-PD with the Disc-criminator™ (sliding aesthesiometer) and completed a CTS questionnaire at baseline, 3, 6, and 12 months, following initiation of AI. Changes in mean 2-PD were analyzed with multivariable mixed effects modelling. A p value < 0.05 was considered statistically significant. Results Of 100 women who underwent baseline 2-PD testing, CTS was identified by questionnaire in 11% at baseline prior to AI initiation. Prevalence of CTS at any time in the first year was 26%. A significant increase in worst 2-PD score was observed from baseline to 3 months (3.7 mm to 3.9 mm, respectively, p = 0.03) when adjusted for age, prior chemotherapy, randomized treatment assignment, and diabetes. There were no significant differences in treatment discontinuation due to CTS between the arms. Conclusion For women receiving adjuvant AI, 2-PD scores were significantly worse at 3 months compared to baseline. Studies are required to assess whether change in 2-PD is an adequate objective assessment for CTS with AI therapy. Early diagnosis of CTS may expedite management, improve AI adherence, and enhance breast cancer outcomes.