Sarcopenia is a prognostic factor for TKIs in metastatic thyroid carcinomas

Purpose Among patients with various cancers receiving anticancer drugs, sarcopenia is associated with poor survival and treatment outcomes. We conducted an observational study using skeletal muscle index (SMI) evaluation to investigate the association between sarcopenia and treatment outcomes of tyrosine kinase inhibitors (TKIs) in metastatic thyroid cancer patients. Methods We included 54 patients (19 men, 35 women; age, 66.5 ± 10.9 years) with differentiated thyroid carcinoma (DTC) or medullary thyroid carcinoma (MTC). The records of patients with metastatic DTC and MTC treated with TKIs were retrospectively reviewed. Patients were divided into sarcopenia and non-sarcopenia groups based on SMI. The SMI cutoff values for sarcopenia were 42 and 38 (cm 2 /m 2 ) for males and females, respectively. Thirty-three patients had sarcopenia before TKI treatment. Results The sarcopenia group had more females and a lower body mass index. The median progression-free survival (PFS) durations were 13.6 (95% confidence interval (CI): 6.1–29.9) and 41.9 (95% CI: 25.2–not estimable) months in the sarcopenia and non-sarcopenia groups ( p = 0.017), respectively. Univariate analysis showed that sarcopenia was significantly associated with PFS ( p = 0.037). Sex, age, and performance status did not affect PFS. Multivariate analysis showed that sarcopenia was the only independent prognostic factor for PFS (hazard ratio: 2.488, 95% CI: 1.058–5.846, p = 0.037). Conclusions Sarcopenia could be a predictive factor of TKI treatment outcomes in patients with metastatic thyroid cancer as well as intervention target to improve prognosis. Further prospective investigations are needed to confirm these preliminary data.