Automated psoas muscle segmentation: imaging features and surgical fitness in spinal metastatic lung cancer

Lung cancer's propensity for spinal metastasis leads to fractures, dysfunction, pain, and reduced quality of life. Spinal interventions are selectively offered to patients deemed fit for surgery. Sarcopenia, assessed by psoas muscle (PM) and whole-abdominal muscle (WAM) measurements, is proposed as a fitness marker, but consensus on thresholds and segmentation tools is lacking. This study aims to validate sarcopenia metrics as imaging biomarkers using both open-source and locally tailored neural networks in the context of bone-metastatic lung cancer and spinal surgery.

A retrospective cohort of 63 lung cancer patients (age 64 ± 9, 46% female) with spinal metastases who underwent surgery between 2010 and 2020 was analyzed. PM and lumbar vertebrae segmentation were validated by a musculoskeletal radiologist on CT scans. A local PM segmentation model was trained using nnUNet, and TotalSegmentator (TS) was used for PM and WAM segmentation. Sarcopenia metrics (i.e., PLVI, PM L4 vertebral index (PLVI), psoas muscle index (PMI), skeletal muscle index (SMI), and total muscle area (TMA)) and radiomic features were evaluated. Survival analysis was conducted based on sarcopenia classification using the Wilcoxon log-rank test.

The locally tailored psoas segmentation model outperformed TS in seven metrics. PMI and PLVI thresholds showed significant survival differences only when measured with the local model (p < 0.05), but not SMI or TMA. Percentile-based classification revealed significant survival differences, especially in local PM metrics (p < 0.001). Of 108 radiomic feature clusters, 38 showed significance with the local models, whereas none did with TS WAM segmentation.

The locally tailored model demonstrated superior performance compared to TS. Percentile-based thresholds and PM features were more predictive of survival, underscoring the need for disease-specific cutoffs. Radiomic features warrant further investigation.

Question Can automated computed tomography assessment of sarcopenia via PM segmentation predict surgical fitness in patients with metastatic lung cancer undergoing spinal surgery? Findings Locally tailored PM segmentations validated known sarcopenia metrics and demonstrated greater significance in predicting patient survival compared to WAM segmentation, using both percentile-based and radiomics features. Clinical relevance The decision to proceed with surgery requires a confident assessment of surgical fitness. As in other surgical contexts, PM sarcopenia assessment through imaging has been validated as a predictor of post-operative survival.