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embargoed access
Embargoed until 2025-06-02
Copyright: Vangelov, Belinda
Embargoed until 2025-06-02
Copyright: Vangelov, Belinda
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Abstract
Background: Assessment of body composition, specifically evaluation of skeletal muscle (SM), has gained momentum in studies of patients with head and neck cancer (HNC). Depletion of SM measured via computed tomography (CT), known as CT-defined sarcopenia, has emerged as an independent prognostic indicator in HNC. International standard SM measures use the cross-sectional area (CSA) of a single axial slice at the third lumbar vertebra (L3). However, diagnostic CT scans for HNC do not always extend to this level, limiting assessment opportunities. This thesis investigates the feasibility of alternate vertebral levels for SM evaluation in HNC.
Methods: A systematic review was undertaken to determine current evidence for SM evaluation at alternate vertebral levels in patients with cancer. Gaps in the literature led to a five phase plan to investigate the use of a cervical (C3) and thoracic (T2) level for SM assessment in patients with HNC who received a diagnostic or radiotherapy planning CT scan. This included evaluation of an existing prediction model (used to estimate L3-CSA with SM at C3), and formulation of population-specific models for use when L3 is not available. Novel methodology for SM evaluation at T2, and thresholds for low skeletal muscle index (SMI) values were also introduced.
Results: The progressive findings of the five studies have indicated that; SM assessment at C3 should be applied with caution; prediction modelling should be population and sex-specific; thoracic SM measures at T2 deplete in similar proportions to L3 over time, cervical SM does not; SM at T2 is predictive of sarcopenia risk (HR=62.78, CI 27.59-164.08, p<0.001); and T2-SMI thresholds for sarcopenia stratified for sex and body mass index were effective in determining patients at risk of critical weight loss during treatments, and overall survival outcomes.
Conclusion: This body of work has identified key concerns with the use of SM at C3 for muscle evaluation in patients with HNC, and has provided evidence for the use of SM at T2 as an alternative to L3. The anatomical position of T2 is not likely to include tumour infiltration, contains musculature that is sensitive to depletion, and is visible in CT scans taken in routine practice for HNC. Population and tumour-specific SMI thresholds for sarcopenia are required in this population for effective diagnosis and appropriate service delivery to ensure optimal nutritional and survival outcomes in this patient population.
