Aerobic Fitness in Breast Cancer Survivors: Association between Sub-maximal and Maximal Cardiopulmonary Exercise Testing

Abstract

Maximal oxygen uptake (Vo2 peak) is a gold standard for peak aerobic fitness and has been used to asses risk for all-cause mortality, cardiovascular disease (CVD), and breast cancer occurrence. Effort during a maximal test may vary in breast cancer patients throughout the continuum of care from diagnosis, during treatment, and until end of post treatment secondary to changing levels of fatigue and treatment tolerance. Sub-maximal exercise testing can be more resilient to symptom fluctuations. PURPOSE: To determine associations between two different sub-maximal testing modalities with a maximal Vo2 peak treadmill test and asses peak aerobic fitness in breast cancer survivors. METHODS: We performed a single maximal cardiopulmonary exercise test (CPET) on a treadmill using indirect calimetry with 30 breast cancer survivors (mean age 50.5 + 5.6 years), while analyzing maximal Vo2 peak. Sub-maximal Vo2 was assessed during the Vo2 peak treadmill test for comparison to the Vo2 peak. A second sub-maximal test on an ARC trainer was conducted for comparison to the treadmill maximal Vo2 peak values. Criteria for both sub-maximal Vo2 tests was established by using the respiratory exchange ratio (RER >1.0) and confirmed upon visual assessment of 1) ventilatory equivalent technique, and 2) modified V-slope method. RESULTS: Vo2 measures for both sub-maximal tests were strongly correlated with the maximal Vo2 peak. Mean values (+ S.D.) with correlation coefficients for maximal and sub-maximal associations were Vo2 peak = 25.4 + 5.3 ml/kg/min compared to; 1) treadmill sub-maximal Vo2 = 20.5 + 4.3 ml/kg/min (r=.83; p=.000), and 2) ARC sub-maximal Vo2 = 19.0 +.26 ml/kg/min (r=.80; p=.000). CONCLUSION: Treadmill and ARC sub-maximal Vo2 exercise tests showed a strong correlation with maximal Vo2 peak, indicating that sub-maximal testing can be a good measure of aerobic fitness in breast cancer survivors. Breast cancer survivors in this study had a marked decrease in Vo2 peak, putting them at a higher risk for all cause mortality, CVD, and breast cancer recurrence. Supported by Back in the Swing and NIH BIRCWH K12 Grant.