Effect of resistance training on natural killer cell activity in women treated for breast cancer treatment : findings from a randomised controlled trial

Background: Previous research has shown that traditional cancer treatments such as surgery, chemotherapy and radiotherapy have a negative impact on immune system functioning. Aerobic exercise has been shown to be beneficial in improving immune function in this population; however, to-date no study has examined isolated resistance training on the markers of immune function and inflammation in this cohort. The purpose of this study was to determine the effect of resistance exercise on the function of natural killer cells in breast cancer survivors. A secondary objective of this study was to determine the effect of resistance training on additional immunological and inflammatory variables, quality of life variables, strength, and body composition. The final objective of this study was to explore potential relationships between primary and secondary outcome measurements. Methods: Thirty-nine breast cancer survivors were randomly assigned to an exercise (n = 20) or a control (n = 19) group. The exercise group trained three times per-week for 16 weeks in a supervised resistance training laboratory gym. The control group did not perform resistance training. The primary outcome for this study was immune function measured through makers of natural killer cell function. Secondary outcomes were additional measurement of inflammation (serum TNF-α, IL-6, IL-10, and CRP), as well as changes in body composition, strength, quality of life, and fatigue. Statistical analysis consisted on the primary outcome consisted of paired and independent T-tests (α < 0.05) conducted according to intention to treat principles. Correlations were utilised to assess relationships as dictated in the third objective. Results: Thirty four women completed the study. Baseline characteristics did not differ between groups except that more women were Caucasian in the control group and more women were taking Arimidex in the exercise group. Intention to treat analysis revealed a significant difference between groups for change in natural killer cell expression of TNF-α (p = 0.004, ES = 1.01). Median CRP concentration in the exercise group reduced -0.5mg/L (IQR -0.35 to 0.08). Median CRP concentration in the control group remained constant (0.00mg/L change, IQR -0.10 to 1.10) There were no other significant differences between groups in any other marker of immune function or inflammation. Intention to treat analysis also revealed significant between group differences for change in QOL as measured by the Functional Assessment of Cancer Therapy - General (p = 0.018, ES 0.79), and fatigue as measured by the Functional Assessment of Cancer Therapy - Fatigue scale (p = 0.011, ES 0.86), and all markers of strength (p