Fast track — ArticlesPrevalence and clinical implications of sarcopenic obesity in patients with solid tumours of the respiratory and gastrointestinal tracts: a population-based study
Introduction
New concepts relating to bodyweight, weight-related disorders, and body composition are emerging in published studies on non-malignant disease. Therefore, the current concept of human bodyweight in patients with cancer might need revision.
WHO categories of body-mass index (BMI) are the reference standard for clinically important human bodyweight strata: ≥40·0 morbid obesity, 35·0–39·9 class II obesity, ≥30·0 class I obesity, 25·0–29·9 overweight, and ≤18·5 for underweight.1 However, these classifications ignore the composition of a unit of weight, which has been shown to be clinically important in many contexts, but which is largely ignored in clinical oncology. Specifically, proportions of fat and lean tissue, especially skeletal muscle, vary widely in current populations.2, 3, 4 Another overlooked concept is sarcopenia (depletion of skeletal muscle), which can occur independently of adiposity. A muscle mass of over two standard deviations below that typical of healthy adults is one current definition of sarcopenia.5 Sarcopenia is associated with physical disability, injuries, and mortality in individuals with non-malignant disease.3, 4, 6 Of interest is sarcopenic obesity, in which severe obesity and low muscle mass occur simultaneously; this condition represents a worst-case scenario because it combines the health risks of obesity and depleted lean mass.7, 8, 9, 10 In this study, we considered that sarcopenic obesity might represent a clinically important body composition type, and we aimed to ascertain its prevalence in a large cohort of patients with solid tumours of the respiratory and gastrointestinal tract who were referred to the Cross Cancer Institute, Edmonton, AB, Canada. We postulated that sarcopenia in obese patients with cancer was significantly associated with low physical ability and to mortality, compared with those who did not have sarcopenia. We also postulated that for patients receiving chemotherapy drugs that are mainly distributed to the lean body compartment, sarcopenic obesity would result in a disproportionately small volume of drug distribution in relation to their bodyweight or body-surface area, as has been implied by previous research.11, 12
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Patients and procedures
A computerised database at the Alberta Cancer Board (Edmonton, AB, Canada) documents information on all primary cancers by their body site and morphology in the province of Alberta, Canada, and provides corresponding biological, clinical, and demographical information for each patient. The institute is the only cancer treatment centre serving northern Alberta (population 1·8 million). The population included all new patients referred to medical oncology clinics at the Cross Cancer Institute
Results
Our initial cohort of 2115 patients included 325 (15%) obese patients. Notably, prevalence of obesity is affected by the trends in weight loss of the population. Many patients reported a history of weight loss in the 6 months preceding the assessment date, and had recently changed BMI category as a consequence. Although 15% of the inception cohort was obese on the assessment date, 6 months earlier 571 (27%) patients had been obese, a decrease of 12%.
Of patients classified as obese, 250 had CT
Discussion
Our study shows the large variability of body composition in obese patients with cancer—information that can be readily obtained from CT images. A substantial proportion (15%) of obese patients in our study had sarcopenia. These patients had exceptionally lower functional status and their sarcopenia was an independent risk factor for poor survival compared with those who were obese and who did not have sarcopenia. Our findings highlight the importance of uncovering a means of treating
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