Longitudinal Body Composition Assessment in Breast Cancer Patients

Skeletal Muscle Mass Index (SMI) is the primary metric for assessing muscle mass. It is a composite value calculated by dividing total skeletal muscle mass (kg), as measured by multifrequency bioelectrical impedance analysis (ACCUNIQ BC720; SELVAS Healthcare), by the square of the participant's height (m2). Weight and height are measured at each time point to calculate this single aggregated value (kg/m2). Higher scores indicate greater muscle mass relative to height (better outcome).Unit of Measure: kg/m2

Handgrip strength of the dominant hand is measured using a hydraulic dynamometer (LiTE - 200 lb Capacity, USA). Participants perform three trials with a 1-minute rest between attempts; the highest (peak) value of the three trials is recorded. Higher scores indicate greater upper extremity muscle strength (better outcome). Unit of Measure: Kilograms (kg)

The 4-meter gait speed (m/s) is measured using a standardized timed walk test. Participants are instructed to walk at their usual pace for 4 meters from a standing start. The time is recorded in seconds and converted to meters per second (m/s). Higher scores indicate faster walking speed (better outcome). Unit of Measure: Meters per second (m/s)

Functional mobility and balance are measured using the Timed Up & Go (TUG) test. The time it takes for a participant to rise from a chair, walk 3 meters, turn around, walk back to the chair, and sit down is recorded. Higher scores (longer time taken) indicate poorer functional mobility and balance (worse outcome). Unit of Measure: Seconds

Lower extremity functional strength is measured as the total number of stands completed in 30 seconds. Participants begin seated and are instructed to stand up and sit down as many times as possible within the 30-second window while keeping their arms crossed over their chest. Higher scores (more stands completed) indicate better lower extremity functional strength and endurance (better outcome). Unit of Measure: Number of stands

Body fat mass (kg) measured using bioelectrical impedance analysis (ACCUNIQ BC720; SELVAS Healthcare). Higher scores indicate greater absolute body fat (worse outcome).

The ratio of total arm lean soft tissue (kg) to total leg lean soft tissue (kg) derived from segmental bioelectrical impedance analysis (ACCUNIQ BC720; SELVAS Healthcare). This ratio is calculated by dividing the sum of lean mass in both arms by the sum of lean mass in both legs. Higher scores indicate a greater proportion of upper limb lean mass relative to lower limb lean mass. Unit of Measure: Ratio

The ratio of total limb lean soft tissue (kg) to trunk lean soft tissue (kg) derived from segmental bioelectrical impedance analysis (ACCUNIQ BC720; SELVAS Healthcare). This ratio is calculated by dividing the sum of lean soft tissue from all four limbs by the lean soft tissue of the trunk. Higher scores indicate a greater proportion of appendicular muscle mass relative to the trunk (better outcome). Unit of Measure: Ratio.

The Overall Edema Index is calculated as the ratio of Extracellular Water (ECW) to Total Body Water (TBW), as measured by multifrequency bioelectrical impedance analysis (ACCUNIQ BC720; SELVAS Healthcare). This index evaluates systemic fluid distribution and edema progression. Higher scores indicate a higher level of extracellular fluid relative to total body water (worse outcome).

Extracellular Water (ECW) measured in liters via multifrequency bioelectrical impedance analysis (ACCUNIQ BC720; SELVAS Healthcare). Unit of Measure: Liters.

Intracellular Water (ICW) measured in liters via multifrequency bioelectrical impedance analysis (ACCUNIQ BC720; SELVAS Healthcare). Unit of Measure: Liters.