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The staging CT scan every cancer patient already has can be measured for muscle and fat at the level of the third lumbar vertebra; low muscle predicts chemotherapy toxicity and shorter survival across cancers, and software now does the measuring automatically.
What it measures. On a single axial CT slice at the third lumbar vertebra, muscle and fat are separated by their density in Hounsfield units. Skeletal muscle area divided by height squared gives the skeletal muscle index; mean muscle density gives myosteatosis (fat within muscle); and visceral and subcutaneous fat areas come from the same slice. Low muscle by sex-specific thresholds is called sarcopenia even when the patient is not thin, and obese patients with low muscle (sarcopenic obesity) have the worst outcomes.
Evidence. Prado and colleagues showed in 2008 (Lancet Oncology) that sarcopenic obesity in patients with lung and gastrointestinal cancers independently predicted survival and that muscle mass, not body surface area, tracked chemotherapy toxicity. Since then hundreds of studies have linked low muscle and low muscle density to complications after surgery, dose-limiting toxicity from chemotherapy and targeted drugs, and shorter survival in most solid tumours. Deep-learning tools now segment the slice in seconds, so the measurement can be produced for every staging scan without extra imaging or radiation.
Who should have it and what changes. It is not yet a guideline-mandated test, but the cachexia and nutrition guidelines already treat body composition as a core assessment, and it is the objective counterpart to nutrition screening questionnaires and hand-grip strength. A finding of sarcopenia should trigger dietitian referral, resistance exercise and, in frail older patients, a full geriatric assessment; some centres use it in surgical risk discussions and in choosing between regimens. Dosing chemotherapy by lean mass rather than body surface area is being tested, not yet standard. The cost is software and reporting time; the scan is free because it has already been done.
Threshold-based or deep-learning segmentation of skeletal muscle, visceral and subcutaneous fat on an axial CT slice at L3, normalised to height and compared with sex-specific cut-offs to classify sarcopenia and myosteatosis.
Query for this technology: (TITLE:"CT body composition and sarcopenia measurement" OR ABSTRACT:"CT body composition and sarcopenia measurement" OR TITLE:"skeletal muscle index" OR ABSTRACT:"skeletal muscle index" OR TITLE:"L3 muscle area" OR ABSTRACT:"L3 muscle area" OR TITLE:"CT sarcopenia" OR ABSTRACT:"CT sarcopenia") AND (cancer OR tumor OR tumour OR oncology OR carcinoma OR lymphoma OR leukemia OR leukaemia OR myeloma OR sarcoma OR melanoma OR glioma). Results are unfiltered search hits about CT body composition and sarcopenia measurement, not a curated reading list.
Shares Measuring muscle and fat on scans the patient already had, Body composition (lean mass, fat mass, visceral fat), Muscle and strength after treatment: sarcopenia, cachexia and what rebuilds, Sarcopenia.
Shares Malnutrition screening tools (MUST, NRS-2002, MST, PG-SGA), Enhanced recovery (ERAS) and perioperative nutrition, Oncology nutrition assessment and medical nutrition therapy, Cancer cachexia.
Shares Body composition (lean mass, fat mass, visceral fat), Muscle and strength after treatment: sarcopenia, cachexia and what rebuilds, Sarcopenia, Geriatric assessment.
Shares Measuring muscle and fat on scans the patient already had, Muscle and strength after treatment: sarcopenia, cachexia and what rebuilds, Sarcopenia, Geriatric assessment.
Shares Sarcopenia, Oncology nutrition assessment and medical nutrition therapy, Cancer cachexia, Nutrition support and cachexia management.
Shares Muscle and strength after treatment: sarcopenia, cachexia and what rebuilds, Cachexia pharmacotherapy: GDF-15 blockade, anamorelin, olanzapine, Cancer cachexia, Geriatric assessment.
Shares Enhanced recovery (ERAS) and perioperative nutrition, Sarcopenia, Nutrition support and cachexia management, Geriatric assessment.
Shares Cachexia pharmacotherapy: GDF-15 blockade, anamorelin, olanzapine, Cancer cachexia, Geriatric assessment, Exercise & lifestyle oncology.
Open-source projects that implement or serve this technology, from OnCo's own catalogue: licence and last activity as the repository reported them on the day of the fetch. Listing is not endorsement; check the licence before reuse and the validation before clinical use.
Segments over a hundred anatomical structures in CT and MRI in one command, widely used for organs at risk and body composition.