The use of routine CT imaging to assess sarcopenia in patients undergoing chemo-radiotherapy for rectal cancer

Abstract

Background Long-course chemoradiotherapy (LCRT) followed by surgery is utilised in patients with locally advanced rectal cancer, but associated with reductions in physical activity, the effects of which are poorly characterised, and increase postoperative complication rates and delay recovery. In previous studies muscle area has been used to measure muscularity; this is the first study measuring muscle volume in addition to area.

Objectives We aimed to determine differences in muscularity between demographic groups prior to LCRT, assess how LCRT affects muscularity and determine if the technique to measure volume is replicable.

Methods Using routine CT images, muscle was differentiated using density measurements, with volume and area calculated by Osirix®. Volume was measured 120 mm above the L5–S1 intervertebral disc, and area at the L3 level. Intra- and inter-observer variability was assessed using six patients, with two patients from each tertile.

Results 38 patients were assessed. Demographic factors affected muscularity (area, volume) prior to therapy, including N stage ( p = 0.019, p = 0.011), gender ( p = 0.0001, p = 0.0001) and age ( p = 0.002, p = 0.0001). Assessment of pre- and post- LCRT scans showed treatment has no effect on muscularity. The technique employed is replicable (concordance correlation coefficient 0.98<).

Conclusions There are significant differences in muscularity between demographic groups prior to therapy, although LCRT was shown to have no effect on muscularity. We also confirmed that the technique employed is replicable and could be used to assess how muscularity impacts on surgical outcomes.