Evaluation of risk factors affecting bone mineral density in breast cancer patients using aromatase inhibitor

Introduction: Breast cancer is the most common cancer in women. While survival time is prolonged with the development of new treatment agents, the incidence of some health problems such as osteoporosis have increased. In this study, we aimed to evaluate the effects of aromatase inhibitors on bone mineral density (BMD) after one year of treatment in women with breast cancer and the possible risk factors that may cause deterioration of BMD in such patients. Materials and Methods: The files of women with breast cancer using aromatase inhibitors between 2008 and 2018 at Inonu University Faculty of Medicine Turgut Ozal Medical Center Medical Oncology Department were retrospectively evaluated. BMD, age, body mass index and vitamin D levels of the patients were analyzed prior initiation and at the end of the first year of treatment. Results: Seventy-five female breast cancer patients were included in the study. In 35 patients who had normal BMD at initiation of treatment, osteopenia developed in 14 patient at the end of a one year treatment period and in 34 patients with osteopenia at initiation of treatment, osteoporosis developed in 6 at the end of a one year treatment period. These changes were statistically significant (p=0.001). Lumbar vertebra and hip T scores before the initiation of anastrozole and letrozole treatment were compared with the scores obtained at the end of the first year of treatment. Lumbar vertebra T score (p<0.001), hip T score (p=0.011) and lumbar vertebra BMD (p<0.001) decreased and the changes were statistically significant. Patients were divided into two groups, as the 'anastrozole group' and the 'letrozole group'. A comparison of lumbar vertebra T score and lumbar vertebra BMD values prior and 1 year after initiation of treatment demonstrated statistically significant decreases in both drug groups. There was a statistically significant decrease in hip T score (p=0.009) in patients receiving letrozole, unlike those receiving anastrazole. Among patients with vitamin D defieciency (<20 ng/mL) at initiation of treatment, lumbar vertebra T score (p<0.001), hip T score (p=0.024) and lumbar vertebra BMD (p<0.001) decreased at the end of 1 year of treatment and these changes were statistically significant. No significant change was observed in BMD of the patients with insufficient (20-30 ng/mL) and sufficient (>30 ng/mL) vitamin D levels. Conclusion: Aromatase inhibitors have a negative impact on bone health in postmenopausal breast cancer patients. In contrast to other patients, these effects were more commonly observed in elderly patients with low vitamin D levels and in obese patients. The present study demonstrates that performing an evaluation of risk factors and taking precations for modifiable risk factors is necessary prior initiation aromatase inhibitor treatment.