Cardiorespiratory fitness in breast cancer patients undergoing adjuvant therapy

The aim of this work was to investigate cardiorespiratory fitness in breast cancer patients at different time points of anti-cancer treatment.

Non-metastatic breast cancer patients (n = 222, mean age 55 years) were categorized into four subgroups according to their treatment status. Cardiopulmonary exercise testing (CPET) was used to measure patients' cardiorespiratory fitness, including oxygen delivery and metabolic muscle function. Testing was performed by bicycle ergometry, and maximal oxygen uptake (VO2peak) was measured. Heart rate during exercise at 50 watts (HR50) was assessed as a cardiocirculatory parameter and ventilatory threshold (VT) was used as an indicator of the O2 supply to muscle. Analysis of covariance was used to estimate the impact of different cancer treatments on cardiorespiratory fitness with adjustment for clinical factors.

Submaximal measures were successfully assessed in 220 (99%) and 200 (90%) patients for HR50 and VT, while criteria for maximal exercise testing were met by 176 patients (79%), respectively. The mean VO2peak was 20.6 ± 6.7 ml/kg/min, mean VT 10.7 ± 2.9 ml/min/kg and mean HR50 112 ± 16 beats/min. Chemotherapy was significantly associated with decreased VO2peak, with significantly lower adjusted mean VO2peak among patients post adjuvant chemotherapy compared to patients with no chemotherapy or those who just started chemotherapy regime (all p < 0.01). Patients post adjuvant chemotherapy reached only 63% of the VO2peak level expected for their age- and BMI-category (mean VO2peak 15.5 ± 4.8 ml/kg/min). Similarly, HR50 was significantly associated with treatment. However, VT was not associated with treatment.

Breast cancer patients have marked and significantly impaired cardiopulmonary function during and after chemotherapy. Hereby, chemotherapy appears to impair cardiorespiratory fitness by influencing the oxygen delivery system rather than impacting metabolic muscle function. Our findings underline the need of exercise training in breast cancer patients to counteract the loss of cardiorespiratory fitness during the anti-cancer treatment.