The present study determined the association of measures of skeletal muscle determined from 18F-FDG PET/CT with health outcomes in patients with soft-tissue sarcoma

Skeletal muscle has a four times higher storage capacity of glycogen compared to the liver and plays a critical role in glycemic control. In metabolic homeostasis, skeletal muscle accounts for 30% of the resting metabolic rate and 80% of glucose disposal under insulin-stimulated conditions.

18F-FDG PET/CT images are routinely acquired for cancer staging, with the primary focus being on tumor assessment and evaluation of the extent of malignant spread. The scan can also be used to opportunistically measure muscle metrics, important for the evaluation of cancer-related cachexia.

In the study, researchers involved 14 patients (8 women and 6 men; mean age 66.5 years) with sarcoma had PET/CT examinations. On CTs of the abdomen and pelvis, skeletal muscle was segmented, and cross-sectional muscle area, muscle volume, and muscle attenuation were determined.

Within the segmented muscle, intramuscular fat area, volume, and density were derived. On PET images, the standardized uptake value (SUV) of muscle was determined. Regression analyses were conducted to determine the association between the imaging measures and health outcomes including overall survival (OS), local recurrence-free survival (LRFS), distant cancer recurrence (DCR), and major surgical complications (MSC).

The association between imaging metrics and pre-therapy levels of serum C-reactive protein (CRP), creatinine, hemoglobin, and albumin was determined. Decreased volumetric muscle CT attenuation was associated with increased DCR. Increased PET SUV of muscle was associated with decreased OS and LRFS.

Our findings in sarcoma patients show that 18F-FDG PET/CT measures are associated with important health outcomes and serum biomarkers. These imaging biomarkers may complement clinical examination of muscle and aid in therapy selection and evaluation.

The opportunistic biomarkers provide an alternative to other techniques used for assessing cachexia such as dual x-ray absorptiometry (DXA), bioimpedance analysis (BIA), and functional testing (e.g., handgrip strength and gait speed). Ultimately, these PET/CT biomarkers could help provide insight into the mechanisms of cancer cachexia and help in identifying disease targets or therapies.

Metabolic information from 18F-FDG PET may complement that gained from CT for the characterization of skeletal muscle. Several skeletal muscle biomarkers could be used as predictors of health outcomes