Sarcopenia as a prognostic factor in gastric cancer patients undergoing gastrectomy: Implications for postoperative and long-term outcomes

Table 1 Computed tomography-based body composition parameters

Parameter	Clinical meaning	Assessment method	Common diagnostic cut-off	Prognostic role	Strengths	Limitations
SMI	Muscle quantity, normalized for body size	Cross-sectional skeletal muscle area at L3 (cm2), indexed to height2 (cm2/m2)	Sarcopenia: < 52.4 cm2/m2 (men), < 38.5 cm2/m2 (women); BMI-adjusted cut-offs also used	Overall survival; predicts chemotherapy toxicity, postoperative complications	Well-validated; single L3 slice correlates strongly with whole-body muscle mass; widely used across cancer/surgical literature	No universal cut-off (varies by ethnicity, population, scanner protocol); requires dedicated software/manual segmentation; height2 normalization may under/overcorrect in obese or very short/tall patients
PMI	Surrogate for muscle mass using a single muscle	Cross-sectional area of bilateral psoas muscles at L3 or L4, indexed to height2 (cm2/m2)	No consensus; commonly cited thresholds approximately < 5.0 cm2/m2 (men), < 3.4 cm2/m2 (women), varies widely by study	Postoperative complications, morbidity	Fast to measure (small, discrete structure); minimal manual tracing needed; feasible even on lower-quality/Limited-slice scans	Poorly correlates with total skeletal muscle mass; high inter-study variability in cut-offs; psoas size affected by positioning and vertebral level chosen; less validated than SMI
SMD	Muscle quality (myosteatosis/fatty infiltration)	Mean CT attenuation (HU) of skeletal muscle at L3	Myosteatosis: < 41 HU (BMI < 25) or < 33 HU (BMI ≥ 25)	Overall survival, independent of muscle quantity	Captures muscle quality, not just size - adds prognostic information beyond SMI; low cost (same CT slice as SMI)	Attenuation affected by CT protocol/reconstruction settings and contrast phase; BMI-stratified cut-offs complicate use; less intuitive for clinicians
VFA	Adiposity, visceral fat burden	Cross-sectional visceral adipose tissue area at L3 (or umbilicus level), cm2	Visceral obesity: ≥ 100 cm2 (women), ≥ 130-163 cm2 (men), varies by study/ethnicity	Postoperative and infectious complications	Strong correlate of metabolic risk and surgical complication risk; reproducible measurement	Cut-offs not standardized across populations; requires accurate delineation from subcutaneous fat; single-slice VFA may not reflect total visceral fat volume
IMAC	Poor muscle quality (fat infiltration within/around muscle)	Ratio of CT attenuation of intramuscular/paraspinal fat to that of paraspinal muscle (using psoas or paraspinal muscles)	No universal threshold; typically defined by cohort-specific median or tertile split	Mortality	Complements SMD; useful when psoas is the only reliably visualized muscle group; correlates with frailty	Lacks standardized cut-off; formula/muscle group varies between studies, limiting comparability; less widely validated than SMI/SMD

SMI: Skeletal muscle index; BMI: Body mass index; CT: Computed tomography; PMI: Psoas muscle index; SMD: Skeletal muscle density; HU: Hounsfield units; VFA: Visceral fat area; IMAC: Intramuscular adipose content.

Table 2 Integrated prognostic models and composite indices in gastric cancer body-composition assessment

Model/index	Main components	Clinical meaning	Prognostic value	Main limitation
GLIM criteria	Phenotypic criteria, including weight loss, low BMI, reduced muscle mass; etiologic criteria, including reduced intake, inflammation, or disease burden	Standardized assessment of malnutrition with body-composition relevance	Identifies patients at higher risk of postoperative morbidity, poor recovery, and worse survival	Requires nutritional and clinical assessment; cut-offs and implementation may vary across populations
GNRI	Serum albumin and body weight relative to ideal body weight	Nutritional risk and systemic reserve	Associated with postoperative complications, treatment tolerance, and long-term survival	Does not directly measure muscle mass or muscle quality
PNI	Serum albumin and lymphocyte count	Combined nutritional and immune status	Predicts postoperative morbidity, recurrence risk, and overall survival	Influenced by inflammation, infection, hydration status, and non-cancer-related conditions
CXI	Skeletal muscle index × serum albumin/neutrophil-to-lymphocyte ratio	Integrates muscle mass, nutrition, and systemic inflammation	May improve risk stratification beyond isolated CT-derived or laboratory markers	Requires standardized CT assessment and laboratory timing
ALBI-related models	Serum albumin and bilirubin, alone or combined with sarcopenia/body-composition variables	Reflects hepatic and nutritional reserve	May help identify patients with impaired physiological reserve and poorer prognosis	More relevant when liver function has prognostic impact; should not be confused with liver-disease scores such as MELD or CTP
Radiomics models	CT texture features from tumor and/or body-composition compartments combined with clinical variables	Imaging-based prediction of recurrence and survival	Can improve individualized prediction beyond conventional staging alone	Requires software, technical standardization, and external validation
AI-based nomograms	Machine-learning or deep-learning features combined with clinicopathological, CT-derived, nutritional, and inflammatory variables	Multivariable personalized risk prediction	May predict postoperative complications, recurrence, and overall survival more accurately than single markers	Limited by retrospective datasets, black-box interpretability, and generalizability across centers
Integrated body-composition scores	SMI, SMD/myosteatosis, visceral fat, sarcopenic obesity, functional tests, and inflammatory/nutritional markers	Multidimensional assessment of host reserve	Captures the combined prognostic impact of muscle quantity, muscle quality, adiposity, and inflammation	Lack of universally accepted thresholds and standardized scoring systems

GLIM: Global leadership initiative in malnutrition; BMI: Body mass index; GNRI: Geriatric Nutritional Risk Index; PNI: Prognostic nutritional index; CXI: Cachexia index; CT: Computed tomography; ALBI: Albumin-bilirubin; MELD: Model for end-stage liver disease; CTP: Child-Turcotte-Pugh; AI: Artificial intelligence; SMI: Skeletal muscle index; SMD: Skeletal muscle density.