A comparison of CT derived body composition at thoracic T4, T12 with lumbar L3 vertebral levels in patients with rectal cancer – which one should we utilise?

Abstract

Abstract Background:Computed tomography (CT) derived body composition measurements of sarcopenia are an emerging form of prognostication in many disease processes. Outcomes in advanced rectal cancer treatment are typically dependent on success of using a combination of chemotherapy and surgery. There is growing evidence that body composition determines chemotherapy tolerance and surgical outcomes. Although the L3 vertebral level is commonly used to measure skeletal muscle mass, other studies have suggested the utilisation of other segments may also be appropriate. This study was performed to determine the variation and reproducibility in assessment of skeletal muscle mass at vertebral levels T4, T12 and L3 in pre-operative rectal cancer patients. Research Methods:118 adult patients with stage I – III rectal cancer, undergoing curative resection from 2010 – 2014, were assessed. CT based quantification of skeletal muscle was used to determine skeletal muscle cross sectional area (CSA) and skeletal muscle index (SMI). Agreement between the measurements at L3 with T4 and T12 vertebral levels were evaluated using goodness-of-fit, Pearson’s correlation coefficient, and Bland-Altman plots.Results:80 of 118 patients were included in our study. There were 21 (26%) female and 59 (74%) male patients (30-86years, Mean±SD; 63.0 ± 13.0). The correlation between SMI at L3 and SMI at T12 was stronger (r = 0.84, P < .001) than that between SMI at L3 and SMI at T4 (r = 0.80, P < .001). Intraclass correlation coefficient was >0.96 at all levels with agreement being highest at T12 and L3. Conclusions:This study demonstrated that quantifying skeletal muscle mass at the T12 vertebral level is straightforward, reproducible, reliable and comparable to measures achieved at L3 in patients with rectal cancer.