Validation of the 6-min Walk Test for Predicting Peak V˙O2 in Cancer Survivors

Abstract

Purpose: To assess the quality of the relationship between V˙O2peak estimated from patient outcomes on the 6-min walk test (6MWT) and the V˙O2peak calculated from patient outcomes on the University of Northern Colorado Cancer Rehabilitation Institute (UNCCRI) treadmill protocol.

Methods: Cancer survivors (N = 187) completed the UNCCRI treadmill protocol and a 6MWT 1 wk apart in randomized order to obtain V˙O2peak. Values from the UNCCRI treadmill protocol were compared against four common 6MWT V˙O2peak prediction equations.

Results: All four 6MWT prediction equations significantly (P < 0.001) underestimated V˙O2peak with predicted values ranging from 8.0 ± 4.1 mL·kg·min to 18.6 ± 3.1 mL·kg·min, whereas the UNCCRI treadmill protocol yielded a significantly higher value of 23.9 ± 7.6 mL·kg·min. A positive strong correlation occurred between estimated V˙O2peak derived from the UNCCRI treadmill protocol and only one of the V˙O2peak values derived from the 6MWT prediction equations (r = 0.81), and all four equations consistently underpredicted V˙O2peak.

Conclusions: These findings suggest that the 6MWT is not a valid test for predicting V˙O2peak in the cancer population due to its consistent underestimation of V˙O2peak regardless of the prediction equation. Obtaining an accurate and valid V˙O2peak value is necessary to correctly prescribe an individualized exercise rehabilitation regimen for cancer survivors. It is recommended that clinicians avoid the 6MWT and instead implement treadmill testing to volitional fatigue to quantify V˙O2peak in cancer survivors.