Muscle strength in breast cancer patients receiving different treatment regimes

Abstract

Background: Muscle dysfunction and sarcopenia have been associated with poor performance status, an increased mortality risk, and greater side effects in oncologic patients. However, little is known about how performance is affected by cancer therapy. We investigated muscle strength in breast cancer patients in different adjuvant treatment settings and also compared it with data from healthy individuals.

Methods: Breast cancer patients (N = 255) from two randomized controlled exercise trials, staged 0-III and aged 54.4 ± 9.4 years, were categorized into four groups according to their treatment status. In a cross-sectional design, muscle function was assessed bilaterally by isokinetic dynamometry (0°, 60°, 180°/s) as maximal voluntary isometric contraction (MVIC) and maximal isokinetic peak torque (MIPT) in shoulder rotators and knee flexors and extensors. Additionally, muscular fatigue index (FI%) and shoulder flexibility were evaluated. Healthy women (N = 26), aged 53.3 ± 9.8 years, were tested using the same method. Analysis of covariance was used to estimate the impact of different cancer treatments on skeletal muscle function with adjustment for various clinical and socio-demographic factors.

Results: Consistently, lower muscle strength was measured in shoulder and knee strength in patients after chemotherapy. On average, patients had up to 25% lower strength in lower extremities and 12-16% in upper extremities in MVIC and MIPT during cancer treatment compared with healthy women. No substantial difference between patient groups in shoulder strength, but significantly lower shoulder flexibility in patients with radical mastectomy was measured. Chemotherapy-treated patients had consistently higher FI%. No serious adverse events were reported.

Conclusions: Breast cancer patients showed markedly impaired muscle strength and joint dysfunctions before and after anticancer treatment. The significant differences between patients and healthy individuals underline the need of exercise therapy as early as possible in order to prevent or counteract the loss of muscle function after curative surgery as well as the consequences of neo-/adjuvant chemotherapy.

Keywords: Chemotherapy; Isokinetic; Isometric; Multi-joint; Muscle function.

Figure 1

Time point of the strength testing in clinically important treatment groups of breast cancer patients and healthy women.

Figure 2

Adjusted means of maximal isokinetic peak torque at 60°/s of extension/flexion knee with 95% confidence intervals. *Significant differences to post neo‐adj. chemotherapy (P = 0.037) and post adj. chemotherapy (P < 0.001); **Significant differences to no chemotherapy (P = 0.0023), post neo‐adj. chemotherapy (P < 0.001), and post adj. chemotherapy (P < 0.001). Models adjusted for age, body mass index (17–<25, 25–30, >30 kg/m²), weight, drugs that influence the muscle tonus, antidepressants, regular cycling, and previous experience in resistance training.

Figure 3

Muscular fatigue over a set and muscular fatigue index (fatigue index = [(peak torque of initial three repetitions−peak torque of final three repetitions)/peak torque of initial three repetitions] × 100) in different treatment groups in knee extensors of the dominant leg. Presented are the unadjusted group means. First repetition omitted from analysis of fatigue index.