151751-Najiba-Chargi

306 CHAPTER 16 DISCUSSION The worldwide incidence of OPSCC is increasing, as is the prevalence of HPV-positive status in OPSCC. The most important prognostic factor in OPSCC is HPV-status; patients with HPV-pos - itive OPSCC have a vastly better prognosis than patients with HPV-negative disease. Over the last decade, low SMM and sarcopenic obesity have emerged as negative prognostic factors in a variety of cancer types and stages. 17,15,30 This study shows that low SMM, sarcopenic obesity and stratification into a high-risk group are associated with impaired survival rates in patients with OPSCC; sarcopenic obesity especially is a negative prognostic factor for overall and disease-free survival in OPSCC, independent fromHPV-status and other factors such as age, BMI, percentage of weight loss 6 months prior to diagnosis, comorbidities and TNM-stage. Pre-treatment low SMM is highly prevalent in patients with OPSCC with an incidence of 64.8%. In contrast, sarcopenic obesity is rare, and occurs in only 6.0% of patients with OPSCC. The individual body composition of cancer pa - tients is increasingly recognized as an important predictive factor for treatment tolerance and for survival after treatment. Specifically, an abnormal body composition with a deficit of SMM with or without a surplus of fat mass (sarcopenia and sarcopenic obesity), is associated with adverse outcomes in oncological patients 31 . Studies in patients with gastrointestinal cancer 32 , lung cancer 33 , breast cancer 34 and pancreatic cancer have shown that patients with sarcopenia or sarcopenic obesity appear to be more prone to experience toxicity of chemotherapeutical treatment and to suffer from complications after surgery.In head and neck cancer patients, recent studies have shown that there is an association between pre-treatment low SMM and chemotherapy dose-limiting toxicity 20 , complications and pharyngocutaneous fistula after total laryngectomy 21,22 , and decreased overall survival. 35 Regarding chemotherapy related toxicity, a hypothesis for this relationship is that patients with low SMM and sarcopenic obesity have a different distribution of chemotherapeutical agents in the body. In terms of compli - cations after surgery, it is hypothesized that patients with sarcopenia may have a decreased capability for recovery, for instance due to an altered protein metabolism or a decreased physiological reserve to deal with surgical stress. In a recent study in advanced oropharyngeal cancer patients, pre-treatment low SMM as a negative prognostic factor in patients with HPV-positive and HPV-negative oropharyngeal cancer showed a trend towards statistical significance. 23 Our study in a larger unselected cohort of OPSCC patients concurs with these results and adds information on the prevalence and prognostic value of sarcopenic obesity in relation to a previous published HPV-related risk stratification model in OPSCC patients. It shows that sarcopenia is highly prevalent in OPSCC patients prior to start of treatment, possibly because oropharyngeal tumors have a high risk of causing dysphagia. 30 The exact mechanisms of sarcopenia and its relationship with adverse outcomes are currently unknown. It is also unknown to which extent the negative effect of sarcopenia can be over -