Evaluation of Pentosidine as Bone Quality Marker in Postmenopausal Breast Cancer Patients Receiving Aromatase Inhibitors

Background: Osteoporosis and fractures are important aromatase inhibitor (AI) related adverse events in postmenopausal women with hormone receptor positive breast cancer. An incremental increase of pentosidine is associated with a deterioration of bone quality. In this study, pentosidine was evaluated in postmenopausal breast cancer patients receiving AIs. Methods: Fifty Japanese postmenopausal breast cancer patients receiving AIs were retrospectively evaluated. Sixteen patients were given a bone modifying agent (BMA) concomitant with AIs. Changes of pentosidine, bone turnover markers and bone mineral density (BMD) before and after 12 months of AI therapy were compared between BMA administered patients (BMA group) and a non-BMA group. These factors were assessed by BMA groups using chi-square of categorical variables and t-test for continuous variables. Results: The median age of the subjects was 67 years, and 21, 23 and 6 subjects were classified as normal, bone loss and osteoporosis, respectively. There was no significant difference between pentosidine low and high groups in regard to age, height, weight, BMD of femoral neck and lumbar spine, and bone turnover markers including TRACP-5b and BAP. In the non-BMA group, pentosidine was increased in 18 cases (53%), and the average change of pentosidine was 21.5% (95%CI; 0.23 to 42.7%, p=0.048). In the BMA group, pentosidine was increased only in 2 cases (13%), and the average change of pentosidine was -16.6% (95%CI; -30.6 to -2.6%, p=0.023). There was a significantly lower proportion of pentosidine-increased cases (p=0.0065) and decrease of pentosidine (p=0.021) in the BMA group compared to those in the non-BMA group. Conclusions: Pentosidine was increased with AI, however, BMA inhibits an AI-induced increase of pentosidine in postmenopausal breast cancer patients.