ESTRO 2021 Abstract Book

S823

ESTRO 2021

cell carcinoma (HNSCC) given the growing interest in sarcopenia as possible negative predictive/prognostic factor for disease progression and survival. Materials and Methods Pretreatment CT scans of HNSCC patients undergoing CRT between January 2010 and December 2017 at our Institution were retrospectively reviewed. Manual segmentation of the skeletal muscle at the level of L3 vertebra was performed using the commercially available software package Osirix. Skeletal muscle area, normalized for squared height to obtain skeletal muscle index (SMI), skeletal muscle density (SMD), and intermuscular adipose tissue area (IMAT) were measured. Low SMD and SMI were defined according to population-specific cut point analysis, and previously reported threshold values (SMD <41 Hounsfield Unit (HU) for Body Mass Index (BMI) <25, <33 HU for BMI >25; SMI <41 in women, <41/<43 in men with different BMI levels). Clinical morphofunctional parameters with known or suspected impact on HNSCC treatment outcomes and sarcopenia were also collected: age, sex, BMI, weight loss in the past 6 months, smoking status, alcohol use, tumor site and grading, human papillomavirus (HPV) p16 status, tumor-node-metastasis (TNM) stage , Charlson Comrbidity Index (CCI), baseline nutritional markers including hemoglobin, leukocytes, C-reactive protein, creatinine and albumin, and treatment intention. Results Preliminary data on the first 69 consecutive patients (among 225 patients included in total) were analyzed. Table 1 summarizes population characteristics. Median age was 70 (59.4-80.7) years, median CCI was 4 (3-7). Patients were planned for 66 to 70 Gy in 30-33 fractions, all but two with rotational intensity-modulated Radiotherapy. Median SMD was 35 (22-45) HU for BMI <25, 37 (20-50) HU for BMI >25; median SMI was 46 (37- 52) for women, >50 (28-70) for men, respectively. Median IMAT was 13 (3-150) cm^2. 1-year and 2-year DFS were 81% and 79%, 1-year and 2-year OS 80% and 65%, respectively (Figure 1A). Patients with SMD <35 HU had lower 1-year and 2-year DFS (both 65%; p=0.003), and 1-year and 2-year OS (68% and 48%, respectively; p=0.001) (Figure 1B). CRT suspension was more frequent for SMD <36 HU (p=0.08). IMAT and SMI did not have an impact on survival. Multivariate analysis showed male sex to correlate with sub-threshold SMD (p=0.02), sex and BMI with SMI below median (p=0.01).