Near infrared spectroscopy (NIRS) as a new non-invasive tool to detect oxidative skeletal muscle impairment in children survived to acute lymphoblastic leukaemia

Background: Separating out the effects of cancer and treatment between central and peripheral components of the O2 delivery chain should be of interest to clinicians for longitudinal evaluation of potential functional impairment in order to set appropriate individually tailored training/rehabilitation programmes. We propose a non-invasive method (NIRS, near infrared spectroscopy) to be used in routine clinical practice to evaluate a potential impairment of skeletal muscle oxidative capacity during exercise in children previously diagnosed with acute lymphoblastic leukaemia (ALL). The purpose of this study was to evaluate the capacity of skeletal muscle to extract O2 in 10 children diagnosed with ALL, 1 year after the end of malignancy treatment, compared to a control group matched for gender and age (mean±SD=7.8±1.5 and 7.3±1.4 years, respectively). Methods and findings: Participants underwent an incremental exercise test on a treadmill until exhaustion. Oxygen uptake ( O2), heart rate (HR), and tissue oxygenation status (Δ[HHb]) of the vastus lateralis muscle evaluated by NIRS, were measured. The results showed that, in children with ALL, a significant linear regression was found by plotting O2 vs Δ[HHb] both measured at peak of exercise. In children with ALL, the slope of the HR vs O2 linear response (during sub-maximal and peak work rates) was negatively correlated with the peak value of Δ[HHb]. Conclusions: The present study proves that the NIRS technique allows us to identify large inter-individual differences in levels of impairment in muscle O2 extraction in children with ALL. The outcome of these findings is variable and may reflect either muscle atrophy due to lack of use or, in the most severe cases, an undiagnosed myopathy