Introduction: Pre-operative exercise training, often referred to as prehabilitation, has been proven safe and beneficial in many clinical cohorts, including those with cancer¹. Despite its origins in anaesthesia where the focus was on improving cardiorespiratory fitness to reduce anaesthetic risk², improving body composition is now a stated aim of many prehabilitation regimes³. Enhancing muscle mass prior to cancer surgery has been shown to improve multiple post operative outcomes including return to normal activities and tolerance of subsequent chemotherapy when needed⁴.

Despite not being the “gold-standard” measure, dual-energy x-ray absorptiometry (DXA) is commonly used and widely accepted as a measure of body composition. However, DXA is not available for this purpose in many (including clinical) settings as it is expensive, requires expert technical support and irradiates subjects. Bioelectrical impedance analysis (BIA), an alternative method to assess body composition ameliorates some of these issues associated with DXA. However, to date, the utility of this method to determine the impact of exercise prehabilitation on body composition of patients with colorectal cancer (CRC) is unknown. Therefore, this study aimed to compare 1) absolute values for body fat percentage (%BF) and leg lean mass (LLM); and 2) the change (Δ) in %BF and LLM, when measured via BIA and DXA in a population with CRC undergoing exercise prehabilitation.

Methods: After receiving favourable opinion from Oxford Research Ethics Committee (23/SC/0115), individuals with confirmed or suspected CRC undergoing surgery with curative intent were randomised to ~4-weeks prehabilitation of: i) high-intensity interval training (HIIT) alone, or ii) HIIT plus resistance exercise training (ReHIIT). Measures of %BF and LLM were made before and after the intervention using both DXA (Lunar Prodigy, GE, UK) and BIA (InBody 770, InBody, UK). Results were analysed using Pearson’s Correlation coefficient, with significance p<0.05⁵.

Results: Twelve individuals were recruited to this study (65+/-8y, 8 male), 5 of whom were randomised to HIIT and 7 to ReHIIT. Pre-intervention BIA data was not available for one participant, with a further two participants missing BIA LLM measures only.

Using pre- and post-intervention data, there was a very strong significant relationship for %BF assessed by BIA compared to DXA (R²=0.96; p<0.001), with a moderate significant relationship for LLM (R²=0.63; p<0.001). Despite this agreement between absolute values, there was no significant relationship between delta change for %BF (R²=<0.001; p=0.96) or LLM (R²=0.37; p=0.08[BP1] ) when comparing the two methods.

Discussion: The results detailed herein suggest that in a population with CRC, absolute measurements of %BF and LLM can be equally determined via DXA and BIA. However, there was no agreement between these methods for change in either of these parameters in response to a prehabilitation regime, suggestive of BIA perhaps not being suitable to determine the effectiveness of such interventions in this cohort.

Future work should confirm these findings with a larger sample size and explore diverse clinical populations. Given the homogeneity of available BIA equipment, alternative BIA equipment should be assessed, ideally against both DXA and the “gold-standard” measure of magnetic resonance imaging (MRI).