{"entity":{"id":"rejuv-measure-body-composition","kind":"technology","name":"Measuring muscle and fat on scans the patient already had","aka":[],"tldr":"A single slice of a CT scan at the third lumbar vertebra measures how much skeletal muscle a person has, and the scan has usually already been taken for staging. Low muscle predicts worse outcomes and more chemotherapy toxicity, including in people whose weight looks normal or high.","summary":"Weight and body mass index are poor measures here, because treatment changes the composition of a body more than its mass. Two people at the same weight can differ by many kilograms of muscle, and the one with less is at the greater risk.\n\nThe method that made this practical. Cross-sectional area of skeletal muscle on a single axial CT image at the third lumbar vertebra correlates closely with whole-body muscle mass and is measurable on scans already taken for staging and response assessment. Prado and colleagues analysed a population-based cohort of 2,115 patients with respiratory or gastrointestinal tract tumours in northern Alberta. Of those, 325 (15 per cent) had a body mass index of 30 or more; 250 of them had analysable images. Sex-specific cut-offs for low muscle were derived by optimum stratification, and 38 of 250, 15 per cent, fell below them. Sarcopenic obesity was associated with worse functional status and was \"an independent predictor of survival (hazard ratio [HR] 4.2 [95% CI 2.4-7.2])\". The reason that paper matters is in its own framing: these were obese patients, and muscle depletion inside obesity is invisible to the scales.\n\nThe other methods. Dual-energy X-ray absorptiometry measures lean mass, fat mass and bone density in one scan and is the reference for bone; it is the scan used to follow treatment-induced bone loss. Bioelectrical impedance analysis is cheap and portable but is affected by hydration, which is a real problem in people having infusions, vomiting or developing oedema. Ultrasound of the quadriceps is emerging for bedside use.\n\nWhy it belongs on a recovery page. Muscle lost during treatment is the thing that makes stairs hard afterwards, and it is the thing resistance training rebuilds. Body composition is how you tell whether it actually came back, and it distinguishes recoverable disuse atrophy from cancer cachexia, which by its own consensus definition cannot be fully reversed by nutritional support while the cancer is active.\n\nWhat it misses. Muscle cross-sectional area is quantity, not quality or strength; a muscle can be infiltrated with fat and perform poorly at normal area, and radiodensity is a partial correction for that. The cut-offs are population-specific and the ones in widest use were derived in North American cohorts, so they transfer imperfectly to Asian and African populations. Software and reader variation between centres is a known source of disagreement. And a CT slice is only available if someone is still having CT scans, which after treatment ends is often no longer the case.","status":"established","asOf":"2026-10-02","wikipedia":"https://en.wikipedia.org/wiki/Body_composition","links":[{"label":"Prado et al., Prevalence and clinical implications of sarcopenic obesity in patients with solid tumours of the respiratory and gastrointestinal tracts: a population-based study (Lancet Oncol 2008)","url":"https://doi.org/10.1016/S1470-2045(08)70153-0"},{"label":"Leong et al., Prognostic value of grip strength: findings from the Prospective Urban Rural Epidemiology (PURE) study (Lancet 2015)","url":"https://doi.org/10.1016/S0140-6736(14)62000-6"}],"tags":["rejuvenation","survivorship","measurement","objective"],"related":["rejuv-measure-cardiopulmonary-exercise-testing","rejuv-measure-consumer-biological-age-tests","rejuv-age-frailty-and-late-effects"],"cancers":["pancreatic","nsclc","gastric","colorectal","esophageal"],"sections":["rejuvenation","supportive-care"],"technologies":["ct-body-composition-sarcopenia","muscle-recovery-after-cancer-treatment","resistance-training-cachexia","oncology-nutrition","cancer-treatment-bone-loss","rejuv-measure-functional-tests"],"targets":[],"drugs":[],"companies":[],"institutions":[],"pathways":[],"terms":["sarcopenia","body-composition","cachexia"],"trials":[],"people":[],"bottlenecks":["b-cachexia-supportive","b-survivorship"],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"principle":"Skeletal muscle and adipose tissue have distinct Hounsfield unit ranges on CT, so a single axial slice at the third lumbar vertebra can be segmented into tissue compartments whose cross-sectional areas scale predictably to whole-body mass, giving a quantitative body composition measurement from an image acquired for another purpose.","strengths":["Uses a scan the person has already had, at no extra dose or cost","Detects muscle depletion that weight and body mass index hide","Independently predictive of survival and of chemotherapy toxicity","The objective counterpart to the strength and performance tests"],"limitations":["Measures muscle quantity, not strength or quality","Cut-offs derived mainly in North American cohorts and transfer imperfectly","Reader and software variation between centres","Needs a CT scan, which stops being taken once follow-up de-escalates"],"since":2008},"route":"/technologies/rejuv-measure-body-composition/","neighbours":{"technology":[{"id":"cancer-treatment-bone-loss","kind":"technology","name":"Bone loss caused by cancer treatment, and what rebuilds it","route":"/technologies/cancer-treatment-bone-loss/"},{"id":"rejuv-measure-cardiopulmonary-exercise-testing","kind":"technology","name":"Cardiopulmonary exercise testing: the hardest number in recovery","route":"/technologies/rejuv-measure-cardiopulmonary-exercise-testing/"},{"id":"ct-body-composition-sarcopenia","kind":"technology","name":"CT body composition and sarcopenia measurement","route":"/technologies/ct-body-composition-sarcopenia/"},{"id":"rejuv-age-frailty-and-late-effects","kind":"technology","name":"Frailty and late effects in survivors","route":"/technologies/rejuv-age-frailty-and-late-effects/"},{"id":"muscle-recovery-after-cancer-treatment","kind":"technology","name":"Muscle and strength after treatment: sarcopenia, cachexia and what rebuilds","route":"/technologies/muscle-recovery-after-cancer-treatment/"},{"id":"oncology-nutrition","kind":"technology","name":"Nutrition support and cachexia management","route":"/technologies/oncology-nutrition/"},{"id":"resistance-training-cachexia","kind":"technology","name":"Resistance training and protein for cachexia and sarcopenia","route":"/technologies/resistance-training-cachexia/"},{"id":"rejuv-measure-consumer-biological-age-tests","kind":"technology","name":"The biological age test you can buy, and whether to buy one","route":"/technologies/rejuv-measure-consumer-biological-age-tests/"},{"id":"rejuv-measure-functional-tests","kind":"technology","name":"Walking, gripping and standing up: the tests that take five minutes","route":"/technologies/rejuv-measure-functional-tests/"}],"cancer":[{"id":"colorectal","kind":"cancer","name":"Colorectal cancer","route":"/cancers/colorectal/"},{"id":"gastric","kind":"cancer","name":"Gastric & gastro-oesophageal junction cancer","route":"/cancers/gastric/"},{"id":"nsclc","kind":"cancer","name":"Non-small-cell lung cancer","route":"/cancers/nsclc/"},{"id":"esophageal","kind":"cancer","name":"Oesophageal cancer","route":"/cancers/esophageal/"},{"id":"pancreatic","kind":"cancer","name":"Pancreatic ductal adenocarcinoma","route":"/cancers/pancreatic/"}],"section":[{"id":"rejuvenation","kind":"section","name":"Recovery & Rejuvenation","route":"/fronts/rejuvenation/"},{"id":"supportive-care","kind":"section","name":"Supportive Care & Survivorship","route":"/fronts/supportive-care/"}],"term":[{"id":"body-composition","kind":"term","name":"Body composition (lean mass, fat mass, visceral fat)","route":"/terms/body-composition/"},{"id":"cachexia","kind":"term","name":"Cancer cachexia","route":"/terms/cachexia/"},{"id":"sarcopenia","kind":"term","name":"Sarcopenia","route":"/terms/sarcopenia/"}],"bottleneck":[{"id":"b-cachexia-supportive","kind":"bottleneck","name":"Cachexia, toxicity and the limits of the patient","route":"/bottlenecks/b-cachexia-supportive/"},{"id":"b-survivorship","kind":"bottleneck","name":"Survivorship and late effects are neglected","route":"/bottlenecks/b-survivorship/"}]}}