CRITERION VALIDITY AND RESPONSIVENESS OF THE STEEP RAMP TEST TO EVALUATE AEROBIC CAPACITY IN CANCER SURVIVORS

A.T.R. Weemaes^1,2, M. Beelen^1,3, B.C. Bongers^2,4, M.P. Weijenberg⁵, A.F. Lenssen^2,1

Background: Insight in aerobic capacity of patients with cancer is important for exercise prescription and evaluation during rehabilitation. The criterion standard to assess aerobic capacity is determining peak oxygen uptake (Vo₂peak) during cardiopulmonary exercise testing (CPET) up to maximal exhaustion. However, performing CPET is not always feasible in daily practice. Previous studies suggest that the steep ramp test (SRT) might be a valid alternative to estimate VO₂peak with the peak work rate (WRpeak) in cancer survivors, but did not investigate its responsiveness.

Purpose: To examine the criterion validity and responsiveness of the steep ramp test (SRT) compared to the cardiopulmonary exercise test (CPET) to evaluate aerobic capacity in cancer survivors participating in a supervised exercise rehabilitation program.  

Methods: Cancer survivors attending a supervised exercise rehabilitation program at Maastricht UMC+ were included in the study. Participants performed a CPET and SRT until voluntary exhaustion before (T=0) and after (T=1) the program. Criterion validity was evaluated at T=0 using Pearson’s correlation coefficients to quantify the relationship between peak work rate achieved during the SRT (SRT-WRpeak) and VO₂peak measured during CPET (CPET-VO₂peak). To examine the responsiveness of the SRT, correlation coefficients were calculated between changes in SRT-WRpeak and CPET-VO₂peak from T=0 to T=1. Moreover, receiver operating characteristic (ROC) analysis was performed to examine the ability of the SRT to detect improvement in aerobic capacity (defined as a relative increase of ≥ 6% in CPET-VO₂peak) and to determine the optimal cut-off value.

Results: One hundred-six participants were included in the study. Mean age was 56.6 ± 11.0 years and breast cancer was the most prevalent diagnosis (48.1%). All participants completed a CPET and SRT at T=0 (N=106) and 55.7% (N=59) completed both tests at T=1. A strong correlation was found for the relation between SRT-WRpeak and CPET-VO₂peak at T=0 (r 0.86). A moderate correlation was found for the relation between changes over time in SRT-WRpeak and CPET-VO₂peak (r 0.51). ROC analysis showed an acceptable responsiveness (area under the curve 0.74) of the SRT to discriminate between participants who did or did not improve CPET-VO₂peak, with an optimal cut-off point of 0.26 W/kg.

Conclusion(s): Results suggest that the SRT is a valid tool to estimate aerobic capacity in cancer survivors. Moderate correlations between change scores indicate that the SRT has a limited responsiveness to measure changes in aerobic capacity. However, ROC analysis implicates that the SRT is able to determine if aerobic capacity has improved or not, when using a cut-off point of 0.26 W/kg. Since breast cancer was the most prevalent diagnosis in this study, further research is needed to confirm our results in patients with other cancer types.

Implications: The SRT can be used to obtain insight in and to detect improvement in aerobic capacity of cancer survivors. A cut-off value of 0.26 W/kg for the SRT-WRpeak could be used to evaluate whether aerobic capacity improved after participating in an exercise program. However, the SRT might not be accurate enough to measure the absolute change in aerobic capacity.

Funding, acknowledgements: This study was unfunded.

Keywords: Exercise testing, Validity testing, Cancer survivors

Topic: Oncology, HIV & palliative care

Did this work require ethics approval? Yes

Institution: Maastricht UMC+ / Maastricht University

Committee: metc azM/UM

Ethics number: 2018-0648