Physical activity among patients with breast cancer receiving aromatase inhibitors is associated with bone health: a cross-sectional observational study.

To examine the association of physical activity (PA) with bone health among patients with breast cancer receiving adjuvant aromatase inhibitor (AI) treatment. In this single-center observational study, we enrolled postmenopausal women with primary hormone receptor-positive breast cancer who were receiving adjuvant AI treatment. We assessed patient bone health [bone mineral density (BMD) and biomarkers of bone turnover] as main outcomes. PA was assessed using Baecke physical activity questionnaires (BPAQ) and an accelerometer. Multiple regression analysis was performed after adjustment for age, body mass index, smoking history and duration of AI treatment. For missing data, multiple imputation analysis was adapted. The mean age of the 53 enrolled patients was 67.4 ± 8.4 years. The mean duration of AI administration was 25.7 ± 18.9 months. The most frequently administered AI was anastrozole (73.6%). Although not related to BMD, PA was related to bone turnover. Serum collagen type I amino-terminal propeptide, a bone formation marker, was associated with only light PA (t =  - 2.55, p = 0.015), while tartrate-resistant acid phosphatase 5b, a bone absorption marker, was associated with work index in the BPAQ subscale and light PA (t =  - 2.28, p = 0.028, t =  - 2.26, p = 0.031, respectively). The results for all patients were similar to those observed in the multiple imputation analysis. PA was significantly associated with bone turnover among cancer patients receiving AI treatment. Light PA and PA in the work domain were the most important factors among various PA intensities and PA domains.