Assessment of Body Composition in Oncology: Moving Research into Practice (Week 4 Lecture 1) Flashcards
What is body composition?
Refers to the amount and distribution of what our bodies are made up of
* Assessment techniques vary by compartments being measured
What are the body composition levels?
- atomic
- molecular
- cellular
- tissues
- whole body
What factors influence body composition?
- genetics
- sex
- race
- growth, pregnancy
- agin
- injury
- illness, disease, and treatment
Why do we want to measure body composition
- independently influences health
- prognostic of clinical outcomes
- Monitor changes associated with dieases [how you come in effects how well you do]
- assess effectiveness of interventions
What is skeletal muscle a criterion for?
- malnutrition
- sarcopenia
- cachexia
Comparison of body comp assessment tools
What does choice of method depend on?
- intended purpose
- patient population
- required accuracy
- precision
- availability
precision vs. accuracy
- accuracy is closeness of the measurement to the true value
- precision is the closeness of measurements to each other
Consensus definition of cancer associated malnutrition
- A multifactorial syndrome of involuntary weight loss (clinical presentation)
- characterized by an ongoing loss of skeletal muscle mass (with or without loss of fat mass) (clinical presentation)
- Due to a variable combination of reduced food intake and abnormal metabolism (etiology)
What are the primary use(s) of CT scans in oncology?
- Determine the size, shape, and location of tumour (staging)
- Determine cancer spread to nearby organs and tissues (staging)
- guide biopsies, and delivery of local treatment
- Plan for delivery of radiation or surgery
- Determine the effectveiness of cancer treatment (compare size of tumour before, during, and after treatment)
- Monitor for recurrence after treatment completed
What is the use of CT scans for body composition?
CT scans are acquired for diagnosis and treatment; never for the sole purpose of assessing body composition
* High risk with radiation
* Costs a lot of resources
How does CT work?
X-rays are attenuated (i.e. absorbed) differently by different body tissues as they pass through and exit the body
* The denser the body tissue the more X-ray energy is absorbed which is referred to as tissue radiodensity (relative inability of X-rays to pass through through a particular material or tissue)
* Taking many measurements from many angles (A full rotation of the x-ray), the different tissue radiodensities are composed as grey scale cross-sectional image using a computer
How is tissue radiodensity expressed?
Hounsfield Units (HU)
* Quantitative scale for describing the radiodensity of different tissues
* different shades of grey represent tissues with different radiodensities
* internal organ will attenuate similar to skeletal muscle so need to know how to differentiate between them
How was CT for body composition assessment validated?
Took skeletal muscle measurements from cross-sectional area of cadaver with CT (and MRI) and validated it with physical measurement.
What CT slice is used to estimate full body composition?
Cross-sectional image at L3
* Best associated to whole body for adipose tissue and skeletal muscle
What tissues are quantified for a body composition assessment?
Adipose tissue
* Visceral adipose tissue (around organs)
* subcutaneous adipose tissue (under skin)
Skeletal muscle
* rectus abdominus
* internal obliques
* external obliques
* transverse abdominus
* psoas
* quadratus lumborum
* lattismus dorsi
* paraspinal (multfidus, iliocostalis, longissimus)
sagittal view
How does CT compare to DEXA?
High correlation but CT provides more information about specific fat tissues and fat-free tissues
What is myosteatosis?
fat infiltration to muscle
* Not really representive of fat in muscle on CT since it is marbled but does tell us about the radiodensity of the muscle → muscle that has low radiodensity is less healthy it is muscle attenuating more like fatty tissue and so quality is not as good.
* multi factorial (T2D, sedentary, HD/ pulmonary conditions)
What data output is retrieved from the CT for body composition?
Cross-sectional areas (cm2)
* skeletal muscle
* visceral adipose tissue
* subcutaneous adipose tissue
* intra-muscular adipose tissue
Tissue radiodensity (HU)
* skeletal muscle
* visceral adipose tissue
* subcutaneous adipose tissue
How is CT used in a research setting?
- To describe variability in body composition
- To identify at risk body composition body types
- To predict clinical outcomes
- To monitor changes over time
How do clinical outcomes differ by oncology setting?
- Early stage cancer: treatment setting = surgery
- Advanced stage cancer: treatment setting = medicial oncology
What are the associations between body composition and clinical outcomes?
Uses stats to define the association with defined cut-offs
* postop/surgical complications
* LOS
* need for rehab care
* 30-day mortality
* readmission
* cancer/tumor recurrence
* treatment toxicity
* physical funcrtion
* QOL
* mortality
What body compositions are considered at risk?
- sarcopenic obesity: ↑ mortality, ↑ surgical complications
- low skeletal muscle mass: ↑ mortality
- Myosteatosis: ↑ mortality
- visceral obesity: ↑ LOS, ↑ operative time
what types of cutoffs are used for body composition from CT to assess clincal outcomes?
cross-sectional areas (cm2; cm2/cm2)
* low skeletal muscle → sarcopenia
* high visceral adipose tissue → visceral obesity
Tissue-specific radiodensity (HU)
* low skeletal muscle radiodensity →myosteatosis
How does sarcopenic-obesity effect mortality?
sarcopenia significantly associated with overall survival
* defined sex-specific cutoffs for CT-defined sarcopenia as <52.4 cm2/cm2 for men & <38.5 cm2/cm2 for women
* defined an at-risk body composition phenotype as sarcopenia obese
What is sarcopenic obesity?
Hidden muscle wasting and its impact for survival and complications of cancer therapy
Prevalence of sarcopenic obesity?
- 9% overall prevalence in advanced solid tumor patients (range 2-15%)
- 1 in 4 obese patients are sarcopenic (range 6-39%)
What are sarcopenic obese at risk for?
- ↑ mortality
- ↑ surgical complications
BMI cut-offs for CT-defined low skeletal muscle mass associated with decreased overall survival
males
* BMI <25; SMI <43 cm2/m2
* BMI >25; SMI <43 cm2/m2
females
* SMI <41 cm2/m2
How
How does mortality change with cancer type wtih low skeletal muscle mass?
increases risk in all types of cancer (colorectal, hepatocellular, pancreatic, gastroesophageal were studied)
* prevalent range 15-50%
What is associated with with mortality acorss cancer types?
- low skeletal muscle mass
- myosteatosis
- sarcopenic obese
How do myosteatosis, visceral obesity & sarcopenia overlap?
Predicts 8 different adverse body composition phenotypes
* 4% have all 3
* 72% have one of these phenotypes
* those with visceral tissue had readmission to the hospital
How does muscle mass diminish with healthy aging?
0.5-1%/ year beginning around age 40 (8%/decade), and accelerates after 70 to about 15%/decade
How might muscle mass diminish in cancer patients?
study done with advanced cervical cancer saw median loss of 5% in 200 days
* 5 years worth of muscle loss
What might be a better tool in identifying low muscle mass for cancer malnutrition instead of an SGA?
CT scan to get more precise skeletal muscle measurements
What indications of the CT scan were benefical for RDs in their practice?
How has knowing about a patients skeletal muscle changed RDs protein reccomendations?
