151751-Najiba-Chargi

85 Diagnostics: cut-off values for low skeletal muscle mass values presented by Prado et al. for patients with solid tumors in which cut-off values of SMM (at L3) were defined by the use of the optimal stratification method for endpoint mortality. 15 This suggests that the cut-off value for low SMM of 2SD belowmean SMM in healthy individuals corresponds with the value of low SMM predictive for mortality in cancer patients. SMM parameters may differ between ethnicities. Although, we do not collect data on ethnicity in our treatment center, majority of patients has a Caucasian ethnicity. Because the cut-off values in our study are therefore mostly representative for the Western-European population, these cut-off values could probably not be extrapolated to other ethnicities. More research is needed to define cut-off values in other ethnic groups and in respect to treatment outcomes in patients with HNC such as surgical complications and dose-limiting toxicities. Our study has some limitations. Firstly, EWGSOP recommended the retrieval of SMM reference values in a healthy population. However, in order to avoid unwanted extra radiation exposure at the head and neck region SMM segmentation on MRI is preferred. MRI of the head and neck region in otherwise healthy people is not routinely performed in clinical practice. Secondly, due to heterogeneity of tumor site, tumor characteristics and tumor stages included in this cohort study, no reliable cut-off value of low SMM for mortality could be provided. Further studies are needed to validate the prognostic impact of the cut-off values for low SMM provid - ed in this cohort. Our study also has some strengths. Firstly, this is the first study providing cut-off values for SMM at the level of C3. Although previous studies provided cut-off values for L3, these cut-off values are usually not applied in HNC research due to the unavailability of abdominal imaging in non-advanced stage HNC. Secondly, we included a large sample size with a large proportion of both female and male patients which strengthens the robustness of the cut-off values that were found. CONCLUSION In this study, cut-off values for low SMM in patients with HNC were presented in order to pro - vide investigators a tool to further explore the association of lowSMM and treatment outcomes in HNC patients. In addition, this tool can also be used for trials investigating interventions to improve SMM in patients with HNC and thereby possibly improve cancer treatment outcomes. 5