Abstract
IntroductionFollowing the consensus definition of cancer cachexia, more studies are using CT scan analysis of truncal muscles as a marker of muscle wasting. However, how CT-derived body composition relates to function, strength and power in patients with cancer is largely unknown. AimsWe aimed to describe the relationship between CT truncal (L3) skeletal muscle index (SMI) and MRI quadriceps cross sectional area with lower limb strength, power and measures of complex function. MethodsPatients undergoing assessment for potentially curative surgery for oesophagogastric or pancreatic cancer were recruited from the regional upper gastrointestinal (UGI) or hepatopancreaticobiliary (HPB) multi-disciplinary team meetings. Maximum Isometric Knee Extensor Strength (IKES) and Maximum Leg Extensor Power (Nottingham Power Rig) (LEP) were used as measures of lower limb performance. Both Sit to Stand (STS) and Timed Up and Go (TUG) were used as measures of global complex muscle function. Muscle SMI was measured from routine CT scans at the level of the third lumbar vertebrae (L3) and MRI scan was used for the assessment of quadriceps muscles. Linear regression analysis was performed for CT SMI or MRI quadriceps as a predictor of each measure of performance. ResultsForty-four patients underwent assessment. Height and weight were significantly related to function in terms of quadriceps power, while only weight was associated with strength (P < 0.001). CT SMI was not related to measures of quadriceps strength or power but had significant association with more complex functional measures (P = 0.006, R2 = 0.234 and 0.0019, R2 = 0.175 for STS and TUG respectively). In comparison, both gross and fat-subtracted measures of quadriceps muscle mass from MRI were significantly correlated with quadriceps strength and power (P < 0.001), but did not show any significant association with complex functional measures. ConclusionCT SMI and MRI quadriceps have been shown to reflect different aspects of functional ability with CT SMI being a marker of global muscle function and MRI quadriceps being specific to quadriceps power and strength. This should therefore be considered when choosing outcome measures for trials or definitions of muscle mass and function.
Highlights
Following the consensus definition of cancer cachexia, more studies are using CT scan analysis of truncal muscles as a marker of muscle wasting
skeletal muscle index (SMI) is commonly reported in the assessment of cancer cachexia, the relationship of muscle area or volume with strength or power is not well described in this patient group
Linear regression analysis was performed for CT SMI or MRI quadriceps cross-sectional area (CSA) as a predictor for each measure of function
Summary
Following the consensus definition of cancer cachexia, more studies are using CT scan analysis of truncal muscles as a marker of muscle wasting. Studies of muscle size and function typically assess strength or power along with CT SMI and volume in specific muscle groups This relationship is well studied in healthy individuals [1,2] and in aging [3], with a clear correlation seen between muscle mass and strength [4,5]. SMI is commonly reported in the assessment of cancer cachexia, the relationship of muscle area or volume with strength or power is not well described in this patient group This question is of particular importance as pain, fatigue and symptoms associated with cancer or cancer treatment, as well as alterations in intramuscular fat, will all affect the functional performance of these patients [7]. This modality is extensively used but has not been validated against function, limb strength and power in patients with cancer
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