The alterations of serum FGF-21 levels, metabolic and body composition in early breast cancer patients receiving adjuvant endocrine therapy.

Background: In early breast cancer patients, the effects of hormonal therapy (tamoxifen and aromatase inhibitors) on plasma fibroblast growth factor 21 (FGF-21), lipid levels and body composition have not yet been investigated. Therefore, we aimed to analyze the relationship between FGF-21 and body composition as well as the effects of tamoxifen and aromatase inhibitors on plasma lipid levels, FGF-21, and body composition.

Methods: A total of 72 patients were treated with either tamoxifen or aromatase inhibitors due to their menopausal status after adjuvant radiotherapy. Each patient was followed-up over a period of 1 year. Changes in body composition and serum lipid profile, glucose and FGF-21 levels were evaluated. We recorded the type of hormonal therapy, body mass index, waist-to-hip ratio, lipid profile, and FGF-21 levels both at the beginning and after 12 months.

Results: There was a statistically significant decrease in serum FGF-21 levels after 12 months of adjuvant endocrine therapy (46 ± 19.21 pg/ml vs. 30.99 ± 13.81 pg/ml, p< 0.001). Total body water (p< 0.001), serum glucose (p= 0.036) and triglyceride levels (p< 0.001) also exhibited a significant decrease. The decreases in total cholesterol and low-density lipoprotein were not statistically significant. Likewise, high-density lipoprotein increased after adjuvant endocrine therapy, although it did not reach statistical significance. The changes in body composition, glucose, lipid profile and FGF-21 were similar in tamoxifen and aromatase inhibitor groups. A positive correlation was found between basal weight, fat mass, fat-free mass and serum FGF-21 levels; however, the correlation was maintained only for the fat-free mass at the 12th month.

Conclusion: As part of the present study, we suggest that both tamoxifen and aromatase inhibitors can reduce FGF-21 levels independently of body compositions, and these drugs can provide antihyperlipidemic, antidiabetic and cardio-protective effects. We also recommend that serum FGF-21 level can be utilized as a tumor biomarker in early-stage breast cancer and for monitoring purposes. FGF-21 levels may help physicians estimate prognosis, too. Further studies with larger populations may shed light on the role of FGF-21 in breast cancer.