Validation of 2 Submaximal Cardiorespiratory Fitness Tests in Patients With Breast Cancer Undergoing Chemotherapy

Patients with breast cancer have an impaired cardiorespiratory fitness, in part, due to the toxic effects of anticancer therapy. Physical exercise as a means of rehabilitation for patients with cancer is an emerging area of research and treatment, emphasizing the need for accurate and feasible physical capacity measurements. The purpose of this study was to evaluate the validity of peak oxygen consumption (o_2peak) predicted by the Ekblom-Bak test (E-B) and the Åstrand-Rhyming prediction model (A-R).

Eight patients with breast cancer undergoing chemotherapy participated in the study. Submaximal exercise tests were performed at 2 different submaximal workloads. Estimated o_2peak values were obtained by inserting the heart rate (HR) from the 2 workloads into the E-B prediction model and the HR of only the higher workload into the Åstrand nomogram. A 20-W incremental cycle test-to-peak effort was performed to obtain o_2peak values.

Results from A-R overestimated o_2peak by 6% (coefficient of variation = 7%), whereas results from E-B overestimated o_2peak with 42% (coefficient of variation = 21%) compared with measured o_2peak. Pearson's correlation coefficient revealed a significant strong relationship between the estimated o_2peak from A-R and the measured o_2peak (r = 0.86; P < .05), whereas the relationship between the estimated o_2peak from E-B and the measured o_2peak resulted in a nonsignificant weak correlation (r = 0.21).

In a situation where maximal exercise testing is not practical or undesirable from a patient safety perspective, submaximal exercise testing provides an alternative way of estimating o_2peak. The A-R prediction model appears to be a valid submaximal exercise test for determining cardiorespiratory fitness in this population.