Validity of Estimated Cardiorespiratory Fitness in Patients With Primary Breast Cancer

Abstract

Background: Estimated peak oxygen consumption (Vo₂peak) is widely used in oncology; however, estimated Vo₂peak equations were developed in noncancer settings.

Objectives: The aim of this study was to evaluate the validity of estimated Vo₂peak in women with primary breast cancer and to develop oncology-specific estimated Vo₂peak equations.

Methods: Vo₂peak was directly measured (TrueOne 2400, Parvo Medics) during 380 cardiopulmonary exercise tests in women previously treated for breast cancer (mean age: 59 ± 10 years; 3.1 ± 1.2 years post-therapy). The American College of Sports Medicine (ACSM), the Fitness Registry and the Importance of Exercise National Database (FRIEND), and heart failure (HF)-FRIEND equations were used to estimate Vo₂peak. New equations were developed using patient and peak (Onc_peak) or submaximal (Onc_sub) exercise test characteristics.

Results: The median differences between measured and estimated Vo₂peak were 7.0 mL O₂·kg^-1·min^-1, 3.9 mL O₂·kg^-1·min^-1, and -0.2 mL O₂·kg^-1·min^-1 for ACSM, FRIEND, and HF-FRIEND, respectively. The number of estimated Vo₂peak values within ±3.5 mL O₂·kg^-1·min^-1 of the measured values was 70 (18%), 164 (43%), and 306 (81%) for ACSM, FRIEND, and HF-FRIEND, respectively. The Onc_peak and Onc_Sub models included body mass index, age, a history of chemotherapy or radiation, the peak measured heart rate, and the treadmill grade and/or speed. The median differences between measured and estimated Vo₂peak were 0.02 mL O₂·kg^-1·min^-1 (Onc_peak) and -0.2 mL O₂·kg^-1·min^-1 (Onc_sub). Eighty-six percent (n = 325) and 76% (n = 283) estimated Vo₂peak values were within ±3.5 mL O₂·kg^-1·min^-1 of the measured Vo₂peak values for Onc_peak and Onc_sub, respectively.

Conclusions: HF-FRIEND or oncology-specific equations could be applied to estimate Vo₂peak in patients previously treated for breast cancer in settings where cardiopulmonary exercise tests are not available. (Trial Comparing the Effects of Linear Versus Nonlinear Aerobic Training in Women With Operable Breast Cancer [EXCITE]; NCT01186367.

Keywords: ACSM, American College of Sports Medicine; BMI, body mass index; CCC, Lin’s concordance correlation coefficient; CPET, cardiopulmonary exercise test; CRF, cardiorespiratory fitness; FRIEND, Fitness Registry and the Importance of Exercise National Database; HF, heart failure; Vo2peak, peak oxygen consumption; breast cancer; cancer survivorship; exercise capacity; peak oxygen consumption.

Graphical abstract

Central Illustration

Measured Versus Estimated Peak Oxygen Consumption in Post-Treatment Primary Breast Cancer (Top) Directly measured peak oxygen consumption (Vo₂peak) using a CPET (n = 380) and estimated Vo₂peak using established equations (American College of Sports Medicine [ACSM], Fitness Registry and the Importance of Exercise National Database [FRIEND], and heart failure [HF]-FRIEND) and oncology-specific equations developed from patient and exercise test characteristics were compared in women previously treated for breast cancer. (Bottom) ACSM and FRIEND equations overestimated Vo₂peak and had poor accuracy compared with cardiopulmonary exercise test (CPET)-measured Vo₂peak. HF-FRIEND and oncology-specific equations could be applied to estimate Vo₂peak in settings where the CPET is not available. Onc_peak = oncology peak; Onc_sub = oncology submaximal.

Figure 1

Bland-Altman Plots of Measured and Estimated Vo₂peak Estimated Vo₂peak from (A) ACSM, (B) FRIEND, (C) HF-FRIEND, (D) Onc_peak, and (E) Onc_sub. The difference between CPET measured Vo₂peak and all estimated Vo₂peak measures along the y-axis and the average of the measured and estimated observations along the x-axis, along with the average bias and 95% limits of agreement. ACSM and FRIEND overestimated Vo₂peak with 95% limits of agreement ranging from −2% to 84% and −6% to 51%, respectively, whereas the limits of agreement were evenly distributed for HF-FRIEND (−20% to 25%), Onc_peak (−20% to 27%), and Onc_sub (−23% to 30%). CPET = cardiopulmonary exercise test; Vo₂peak = peak oxygen consumption; ACSM = American College of Sports Medicine; FRIEND = Fitness Registry and the Importance of Exercise National Database; HF = heart failure; Onc_peak = oncology peak; Onc_sub = oncology submaximal.

Figure 2

Concordance Plots of Measured and Estimated Vo₂peak Difference between CPET measured Vo₂peak and estimated VO₂peak from (A) ACSM, (B) FRIEND, (C) HF-FRIEND, (D) Onc_peak, and (E) Onc_sub. The concordance estimated and measured Vo₂peak was evaluated by Lin’s concordance correlation coefficient (CCC). A CCC value of 1 indicates perfect agreement; values <0.6 were considered to be poor agreement. There was a low CCC between measured and ACSM and FRIEND estimated Vo₂peak and a high CCC between measured and HF-FRIEND, Onc_peak, and Onc_sub. Abbreviations as in Figure 1.