TY - JOUR T1 - <strong>Pretherapy Muscle 18F-FDG uptake: association with outcome in advanced head and neck cancer</strong> JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 3107 LP - 3107 VL - 63 IS - supplement 2 AU - Esraa Roshdy AU - Tayseer Ahmed AU - Yasser Abdelhafez Y1 - 2022/06/01 UR - http://jnm.snmjournals.org/content/63/supplement_2/3107.abstract N2 - 3107 Introduction: Skeletal muscle FDG uptake is affected by numerous physiologic and pathologic processes. In cancer patients, increased systemic inflammation has been associated with cancer outcomes. Also, browning of adipose tissue, including the fat in the inter- and intra-muscular compartments, could be linked to cancer cachexia and subsequently prognosis. The effect of these two mechanistic pathways may lead to changes in FDG uptake in skeletal muscles.On the other hand, numerous reports showed that low-dose CT muscle metrics, like surface area and mean attenuation, derived from abdominal circumference at the level of 3rd lumbar vertebra (L3) are associated with outcome in cancer patients. However, the opportunistic exploration of the corresponding 18F-FDG PET metrics has been scarcely reported.&amp;nbsp;Our aim is to explore the potential prognostic role of 18F-FDG uptake in L3 muscles of patients with head and neck squamous cell carcinoma (HNSCC).Methods: Retrospective review of 18F-FDG PET/CT data retrieved from Cancer Imaging Archives. A total of 103 patients with advanced clinical stage HNSCC (stage III &amp;amp; IV), treated with radiotherapy with or without chemotherapy, who underwent pre-therapy whole body 18F-FDG PET/CT scan were included. Abdominal circumference muscles at L3 level were delineated on the low-dose CT component of the PET/CT at a threshold between -29 and 130 HU. CT mean muscle attenuation (MMA) in HU and skeletal muscle area (SMA) in square centimeters were obtained. SMA was divided by the square of height to obtain Skeletal Muscle Index (SMI) in cm2/m2. Mean SUV of the muscles at the same level was calculated then normalized to blood pool measured at the ascending aorta to obtain SUV ratio expressed as a percentage (rSUV).All patients had a minimum follow-up of 24 months or till recurrence or death.&amp;nbsp;The primary endpoint was disease free survival (DFS) defined as time to first recurrence/residual disease confirmation or censoring at their last follow-up. The secondary endpoint was disease-specific survival (DSS), defined as time to death from cancer or censoring at their last follow-up.&amp;nbsp;Univariate (UVA) and multivariate (MVA) Cox regression analyses were used to identify continuous variables associated with survival.Results: After a median follow-up of 81 months, 83 were disease free and 20 patients experienced treatment failure in different patterns (3 local recurrence, 5 residual local disease, 2 neck nodal recurrence, 8 isolated distant metastasis, 1 regional and distant, and 1 locoregional and distant failures). Of the 20 patients, 14 died of cancer resulting in DSS of 87%.On UVA, DFS was not associated with CT metrics; either MMA (Hazard ratio[HR]=0.96, 95%confidence interval [CI]: 0.91-1.01, P= 0.12) or SMI (HR=0.97, 95%CI:0.92-1.01; P=0.13). However, both metrics showed significant association with DSS (respectively, HR=0.92, 95%CI=0.86-0.98; P=0.007 and HR=0.94, 95%CI=0.90-1.0; P=0.03)On the other hand, rSUV demonstrated significant association with DFS (HR=1.03, 95%CI: 1.01-1.05; P=0.001) but not with DSS (HR=1.01, 95%CI: 0.99-1.04; P=0.3).rSUV showed weak-to-moderate, yet significant, negative correlations with MMA (rho=-0.21, 95%CI=-0.39 to -0.03) and SMI (rho=-0.36, 95%CI=-0.52 to -0.18).on MVA, and after adding the interaction terms, rSUV and its interaction with MMA were the only significant predictors of DSS (respectively, HR=1.3, 95%CI: 1.02-1.62; P=0.03 and HR=0.99, 95%CI=0.99-1.0;P=0.03).Conclusions: Skeletal muscle metrics obtained from both PET and CT components of pretherapy 18F-FDG PET/CT may provide important prognostic information in patients with advanced stage head and neck cancer. This opportunistic information may be used to tailor lifestyle or nutritional interventions. Further validation of the current findings in larger cohort is warranted. ER -