Monitoring aerobic capacity in cancer survivors using self-reported questionnaires: criterion validity and responsiveness.

Background: Evaluating the criterion validity and responsiveness of the self-reported FitMáx©-questionnaire, Duke Activity Status Index (DASI) and Veterans Specific Activity Questionnaire (VSAQ) to monitor aerobic capacity in cancer survivors.

Methods: Cancer survivors participating in a 10-week supervised exercise program were included. The FitMáx©-questionnaire, DASI, VSAQ and a cardiopulmonary exercise test (CPET) were completed before (T) and after (T) the program. Intraclass correlation coefficients (ICC) were calculated between VO estimated by the questionnaires (questionnaire-VO) and VO measured during CPET (CPET-VO), at T to examine criterion validity, and between changes in questionnaire-VO and CPET-VO (ΔT-T) to determine responsiveness. Receiver operating characteristic (ROC) analyses were performed to examine the ability of the questionnaires to detect true improvements (≥ 6%) in CPET-VO.

Results: Seventy participants were included. Outcomes at T were available for 58 participants (83%). Mean CPET-VO significantly improved at T (Δ1.6 mL·kg·min or 8%). Agreement between questionnaire-VO and CPET-VO at T was moderate for the FitMáx©-questionnaire (ICC = 0.69) and VSAQ (ICC = 0.53), and poor for DASI (ICC = 0.36). Poor agreement was found between ΔCPET-VO and Δquestionnaire-VO for all questionnaires (ICC 0.43, 0.19 and 0.18 for the FitMáx©-questionnaire, VSAQ and DASI, respectively). ROC analysis showed that the FitMáx©-questionnaire was able to detect improvements in CPET-VO (area under the curve, AUC = 0.77), when using a cut-off value of 1.0 mL·kg·min, while VSAQ (AUC = 0.66) and DASI (AUC = 0.64) could not.

Conclusion: The self-reported FitMáx©-questionnaire has sufficient validity to estimate aerobic capacity in cancer survivors at group level. The responsiveness of the FitMáx©-questionnaire for absolute change is limited, but the questionnaire is able to detect whether aerobic capacity improved. The FitMáx©-questionnaire showed substantial better values of validity and responsiveness compared to DASI and VSAQ.