151751-Najiba-Chargi

15 Introduction improvements in surgical techniques and advances in radiotherapy have also contributed to preservation of function and reduced morbidity and mortality. Despite intensive treatment, the prognosis of head and neck cancer patients is generally poor. The 5-year overall survival of patients with HNSCC is largely dependent on disease stage. Locally advanced diseases have a poor prognosis with a 5-year overall survival less than 50%. 22 Asmentioned earlier, HPV-related head and neck cancers have a distinct behavior and an overall better prognosis. The 3-year survival of HPV-positive tumor patients is better than HPV-negative patients, 82% versus 57%, respectively (p< 0.001). 8 Due to increased prevalence of HPV-related tumors and increased treatment advances, the number of survivors of HNSCC rises. Patients with HPV-related can - cers can be divided in three risk groups based on smoking habits and the T or N stage with different 3-year overall survival rates: 94% for the low risk, 67% for the intermediate risk and 42% for the high risk group. 8 In 2017, the AJCC and the Union for International Cancer Control (UICC) introduced a separate staging system for patients with HPV-positive oropharyngeal carcinoma in recognition of the improved prognosis. 11,23 PREDICTORS AND PROGNOSTICATORS IN HEAD AND NECK CANCER As mentioned earlier, TNM stage and HPV-status are major prognosticators for survival in patients with head and neck cancer. It is also known that incompletely resected or inoperable tumor carry a worse prognosis. For surgically treated patients, involvement of the resection margin (R1) at the primary site or extracapsular spread at different levels of lymph nodes are independent prognostic factors for overall survival in HNSCC. 11 However, for HPV-related oro - pharyngeal carcinoma, extracapsular spread and advanced nodal stage are not predictive for local recurrence, whereas patients with positive tumor margins, 5 or more neck node metas- tases and a T stage of 3 or 4 are identified as a high-risk population. 24 It has also been shown that the type of surgery used to treat HNSCC may also be an important prognostic factor in HNSCC outcomes. 25 Nevertheless, stage-dependent differences in outcomes have been consis - tently over the past two decades, despite the development of risk-adapted curative treatment strategies. 26 Novel strategies are thus needed to change the focus from uniform treatment for all patients with the same TNM stage, clinical and histological features to a personalized treatment guided by biomarkers that identify individual differences between patients. AN EMERGING PREDICTIVE AND PROGNOSTIC BIOMARKER IN THE FIELD OF CANCER: SARCOPENIA Over the last decade, research on body composition has gained increased attention in onco - logical and surgical literature. Body composition consists of fat mass and fat-free mass also called lean body mass. The skeletal muscle mass is the largest contributor to the lean body mass. 27 Low skeletal muscle mass is also referred to as sarcopenia. Sarcopenia lends its name from the Greek words ‘’sarx’’ meaning flesh and ‘’penia’’ meaning lack of. Sarcopenia can be primary due to ageing and secondary due to an underlying disease. The proposed definition of sarcopenia of the European Working Group on Sarcopenia in Older People (EWGSOP) requires a decrease in skeletal muscle mass and a decrease inmuscle function. 28 Muscle function is not routinely measured; therefore, the terms sarcopenia and low skeletal muscle mass are often 1