Endocrine Abstracts

Objective: Recent studies have shown that sarcopenia at cancer diagnosis is associated with a poor survival in patients with solid tumors. Up to now, few data are available among patients with advanced thyroid cancer, especially those treated with tyrosine kinase inhibitors (TKI). We retrospectively evaluated sarcopenia by Skeletal Muscle Index (SMI) in a cohort of advanced thyroid cancer patients before and during TKI treatment and investigated its association with treatment outcome.

Methods: Fifty-eight patients (28 females and 30 males age at the time of TKI treatment 67.5±13.8 years) with advanced thyroid cancer were divided into Sarcopenia (SG) and Non-Sarcopenia Groups (NSG) based on SMI values. SMI was measured by CT as the cross-sectional area of skeletal muscles at the third lumbar vertebra level, normalized by height squared (cm²/m²). Radiological evaluation was performed at baseline and on average every 3-6 months thereafter. Response to treatment was assessed according to the Response Evaluation Criteria in Solid Tumors v.1.1.

Results: The prevalence of pre-treatment sarcopenia was 20.7% and it was correlated with Body Mass Index (23.8±3.7 kg/m² SG vs 28.2±6.1 kg/m² NSG, P=0.004), BMI categories (P=0.01) and duration of first TKI treatment (19.1 months SG vs 28.78 months NSG, P=0.012). A significant reduction in SMI values was observed already after 3 months of treatment (P=0.002) and still after approximately 1 year of therapy (P<0.0001). At the end of the period of observation sarcopenia prevalence was 38.5%. The development of 12 months-sarcopenia was predicted by a lower SMI (P=0.029) BMI (P=0.02) and weight (P=0.04) and by presence of bone metastases (P=0.02). The best basal SMI cut-offs able to predict sarcopenia occurrence were 37.6 cm²/m² (AUC=0.94 95% CI: 0.8358-1; P<0.0001) for females and 51.4 cm²/m² (AUC=0.88 95% CI: 0.697-1; P<0.0001) for males; the best BMI cut-off was 26.5 kg/m²(AUC=0.920, 95% CI: 0.586-0.932, P=0.003). The median progression-free survival (PFS) was 8.46±6.87 months and 24.39±18.96 months in SG and NSG (P=0.008), respectively. At multivariate analysis, pre-treatment sarcopenia significantly affected treatment outcome, resulting the parameter that has the greatest impact on PFS (HR 4.29; 95% CI, 1.21–15.11, P=0.02).

Conclusions: This is the first study that evaluated sarcopenia prevalence and its change over time in Caucasian patients with advanced thyroid cancer under TKI therapy. Sarcopenia seems to be a prognostic factor of TKI treatment outcome, suggesting the importance of the assessment of the nutritional status and body composition in advanced thyroid cancer patients.