Purpose: To accurately assess exercise interventions and to evaluate acute and chronic cardiovascular effects in patients with early-stage cancer, consistently reliable functional outcome measures must be obtained. An incremental cardiopulmonary exercise test (CPET) with gas exchange measurement to assess peak oxygen consumption (V˙O2peak) provides the gold standard outcome of cardiorespiratory fitness.
Methods: In the context of a randomized controlled trial, 40 patients with prostate cancer (mean age, 59 ± 7 yr) after radical prostatectomy performed two maximal CPET within 5.6 ± 5.5 d of each other. Incremental treadmill tests were performed in the morning under identical laboratory conditions. Reliability and within-subject variability from test 1 to test 2 for peak and submaximal variables were assessed by correlation coefficients, intraclass correlations (ICC), Bland-Altman plots, coefficient of variation, and paired t-tests.
Results: There was high reliability between CPET for V˙O2peak (r = 0.92; P < 0.001; ICC, 0.900), ventilatory threshold (r = 0.88; P < 0.001; ICC, 0.927), minute ventilation-carbon dioxide production relation (V˙E/V˙CO2) (r = 0.86; P < 0.001; ICC, 0.850), and peak heart rate (r = 0.95; P < 0.001; ICC, 0.944). However, high within-subject variability was observed for all CPET parameters (mean coefficient of variation, 4.7%). Compared with those for test 1, significantly higher mean values were observed for V˙O2peak (27.0 ± 5.6 vs 28.1 ± 5.3 mL·kg·min, P < 0.05), ventilatory threshold (1.91 ± 0.5 vs 1.97 ± 0.4 L·min, P < 0.05), and V˙E/V˙CO2 (31.3 ± 5.8 vs 32.8 ± 3.4, P < 0.05) in test 2.
Conclusions: These findings indicate the presence of significant, and potentially clinically important, variability in CPET procedures in men with clinically localized prostate cancer and have important implications for the application and use of CPET to evaluate the efficacy of interventions to improve aerobic capacity in the oncology setting.