ESTRO 2021 Abstract Book

S802

ESTRO 2021

(≥30ng/mL), insufficient (10-30ng/mL) or deficient (<10 ng/mL). Serum VitB12 level was defined normal if in the range 200-900 ng/mL. During RT course, toxicity was assessed every week by the radiation oncologist with clinical examination and flexible fiberoptic laryngoscopy to define acute mucositis and dermatitis and weight loss as well. Acute toxicity was defined as the highest grade developed during RT according to CTCAE v5.0. Results Eleven patients (10.8%) reported normal VitD level, whereas 68 (66.7%) and 23 (22.6%) patients had insufficient or deficient level, respectively. VitD deficiency was more frequent among current smokers (39.4% vs. 13.4%; p=0.013), but not among current drinkers (26.1% vs. 19.2%; p=0.730). Variation in VitD level during treatment was negligible (median variation: -0.2 ng/mL; IQ range: -2.6 to 1.5 ng/mL). G3-G4 mucositis was reported in 41 patients (40.2%), G3-G4 dermatitis in 21 (20.6%), and weight loss>10% in 17 (16.7%). No acute toxicity was associated to baseline VitD level. All patients but 7 (6.9%) reported normal VitB12 levels. However, patients with VitB12 levels below median level (i.e., 450 ng/mL) showed higher frequency of acute G3-G4 mucositis (53% vs. 31.3%; p=0.037) than those with higher VitB12 level; although not statistically significant, acute dermatitis (27.9% vs. 13.0%) and weight loss>10% (22.2% vs 10.4%) were more frequent among patients with VitB12 <450ng/mL. Conclusion Our preliminary results suggest that baseline serum VitD levels are not associated with the risk of acute radiation-induced toxicity in our cohort, while lower levels of VitB12 might predict higher incidence of acute toxicity and mainly mucositis. PO-0966 Sarcopenia as prognostic marker in elderly HNSCC patients undergoing (chemo-)radiation E. Haehl 1 , L. Alvino 1 , A. Rühle 1 , T. Sprave 1 , A. Grosu 1 , N.H. Nicolay 1 1 University of Freiburg - Medical Center, Department of Radiation Oncology, Freiburg, Germany Purpose or Objective Sarcopenia is associated with reduced survival and vulnerability to toxicity in malignant diseases including squamous cell carcinoma of the head and neck (HNSCC). The prevalence of sarcopenia increases with age and is an important cause of functional decline in the elderly. We evaluated the influence of pretherapeutic sarcopenia in elderly HNSCC patients undergoing (chemo-)radiation regarding oncologic outcomes and therapy- related toxicities. Materials and Methods Skeletal muscle mass as an indicator for sarcopenia was outlined and quantified on pretherapeutic treatment planning CT scans at the level of the third cervical vertebra (C3MA) in 282 HNSCC patients aged > 65 years undergoing (chemo-)radiotherapy in our institution from 2010 to 2019. Using a previously published formula, C3MA was converted to the cross-sectional muscle area at the third lumbar vertebra (L3MA) and normalized for height (L3MI). After sex-specific standardization, L3MI and L3MA were correlated with clinical parameters. After dichotomization into “sarcopenic” and “non-sarcopenic” patients based on published standards, frequency distributions for clinical parameters as well as oncologic outcomes such as overall survival (OS), progression-free survival (PFS) and locoregional control (LRC) were calculated. The prognostic value of sarcopenia was analyzed using the Cox proportional hazards model. Results Patients deemed sarcopenic had significantly larger tumors (T3/4 53.6% vs 67.5%, p =0.001) and a significantly higher comorbidity index (4.2 vs 4.8, p = 0.049). Patients with low LM3I had significantly more severe acute toxicities (CTCAE grade 4 9.1% vs 3.6%, p =0.017). OS and PFS differ significantly between sarcopenic and non- sarcopenic patients with a median of 24 vs 47 months ( p =0.002) and 13 vs 47 months ( p =0.001), respectively. In the multivariate analysis, low LM3I as an indicator for sarcopenia was a significant prognostic factor deteriorating OS (HR 1.56, CI 1.04-2.35, p= 0.033). OS was also influenced by patients’ performance status ( p <0.001) and smoking history ( p =0.012). Continuous values of L3MA and L3MI significantly correlated with the pretherapeutic hemoglobin level (rho=0.258, p <0.001 and rho= 0.208, p =0.001). Further, LM3I negatively correlated with patient age (rho=-0.21, p <0.001), CCI (rho=-0.13, p =0.029) and severity of acute toxicities (rho=-0.126, p =0.035). Conclusion Sarcopenia deduced from low skeletal muscle mass is a significant prognostic factor in elderly patients with HNSCC undergoing (chemo-)radiation and should be taken into account in clinical decision-making. Its role as a predictive marker for tailored supportive interventions such as physical therapy or nutrition counseling needs to be evaluated prospectively. PO-0967 Factors associated with feeding tube requirement in Oropharyngeal Cancer treated with IMRT. O. Monaghan 1 , N. O'Dwyer 2 , M. Dunne 3 , J. Nugent 2 , N. Coughlan 2 , A. Nolan 2 , F. Gilbert 4 , A. Glynn 2 , F. Duane 4 , C. Parkes 4 , S. Brennan 4 1 st lukes radiation oncology network, radiation oncology, dublin, Ireland; 2 St lukes Radiation oncology network, Radiation oncology, dublin, Ireland; 3 Radiation oncology, Radiation oncology, dublin, Ireland; 4 St lukes Radiation oncology network, Radiation oncology, Dublin, Ireland Purpose or Objective Patients with oropharyngeal cancer commonly require nutritional support when undergoing radical radiotherapy (+/- chemotherapy). In line with international guidelines our policy is for reactive tube insertion using a nasogastric tube (NGT) but where patients have low functional oral intake scale (FOIS) and significant weight loss a prophylactic gastrostomy tube is inserted. This study aims to identify differences in nutritional management for patients with HPV(-)disease versus HPV(+) disease and to identify factors associated with feeding tube requirements. Materials and Methods