151751-Najiba-Chargi

299 Systemic therapy: skeletal muscle mass and oropharyngeal carcinoma RESULTS A total of 216 OPSCC patients with curative treatment intent and adequate pre-treatment imaging of the head and neck area at the level of C3 were included. Of these patients, 174 patients were identified with known HPV-status. RISK-STRATIFICATION ACCORDING TO HPV-STATUS Patients within the high-risk group had a statistically significant worse median OS and DFS (27 months; IQR 12-50 and 20 months; IQR 9-46 respectively) compared to patients within an intermediate risk group (47 months; IQR 38-63 and 47 months; IQR 26-63 respectively) and low risk group (45 months; IQR 22-62 and 44 months; IQR 16-62 respectively) (high versus intermediate risk: Log Rank χ 2= 20.02; p<0.01 and high versus low risk: Log Rank χ 2= 16.61; p<0.01). Patients within a high-risk group had a significantly worse 5-year OS and DFS rate (32%and 50%, respectively) compared to patients within an intermediate risk group (74%and 80%, respectively) (p<0.01) and low risk group (72% and 87%, respectively) (p<0.01). As shown in table 2 and 3; univariate Cox regression analysis showed that stratification into a high-risk group was statistically significant associated with a decreased OS (HR 3.11; 95% CI 1.61-6.01, p<0.01) and DFS (HR 4.85; 95% CI 1.89-12.42, p<0.01). When corrected for multiple, potentially interacting variables by multivariate Cox regression analysis; stratification into a high-risk group remained of significant negative prognostic value for OS (HR 2.31; 95% CI 1.14-4.68, p<0.05) and DFS (HR 4.06; 95% CI 1.52-10.84, p<0.01). BODY COMPOSITION Endpoint-specific cutoff values for L3 muscle mass indices were determined at 43.0 cm 2 /m 2 for OS and 43.2 cm 2 /m 2 for DFS. These cut-off values are comparably with previous cutoff values established in a separate cohort of head and neck cancer patients. 20 Using these cutoff values, 140 patients (64.8%) were identified with low SMM and 13 patients (6%) were identified with sarcopenic obesity. Clinical and demographic characteristics of patients with and without low SMM are listed in table 1. Statistically significant differences between patients with and without low SMMwere seen in sex, age at diagnosis, percentage of weight loss within six months prior to diagnosis, body-mass-index, number of pack-years, HPV-status and HPV risk group. Patients with low SMM were more likely to be female (50.7% versus 2.6%; p<0.01), to be older of age at diag - nosis (mean 63.6 years versus 60.3 years; p<0.05), to have 10% or more weight loss in the six months prior to diagnosis (15% versus 7.9%, p<0.05), to have a BMI that is less than 20kg/m 2 (28.6%versus 2.6%; p<0.01), to have smoked for more than 41 pack-years (40.3%versus 22.2%; p<0.05), to have a HPV-negative related tumor (55% versus 36.8%; p<0.01) and to be stratified within a high-risk group (39.1% versus 13.8%; p<0.01). 16