METRIC studie (WC 2012-031)


Starting date: 07/08/2014

Although great improvements in disease free and overall survival rates are achieved after (neo-) adjuvant systemic therapy, cancer survivors (defined as patients following first diagnosis, until the end of life) often experience negative side effects of cancer and cancer treatment, with fatigue and a decrease in Quality of Life (QoL) as the most common distressing symptoms. Physical activity during and after cancer treatment has beneficial effects on a number of physical and psychosocial outcomes, including increased aerobic fitness, reduced fatigue and depression, and improved health related quality of life (HRQoL). 

Physical activity levels of cancer survivors are lower than in the general population, and they tend to decline during cancer treatment and remain lower for years after cancer treatment. Objective measurement of both physical activity and sedentary behavior can be obtained using accelerometers. Following data reduction procedures, time spent in sedentary, light, moderate or vigorous physical activity behavior are subsequently assessed by applying cut-points. As these cut-points are validated in the general population, which generally have a higher fitness level, they may not be appropriate for cancer survivors. Therefore, alternative cut-points or innovative predictions of accelerometer-based physical activity and sedentary behavior may be required to capture the pattern of both physical activity and sedentary behaviour in cancer patients. 

Possibly, demographic, clinical, physical and psychosocial variables are associated with physical activity levels and sedentary behaviour. Knowledge of the correlates of physical activity and sedentary behaviour could help to develop more suitable and effective exercise interventions, thereby increasing physical activity levels in cancer survivors. Insight in patterns of physical activity and sedentary behaviour could also help to more accurately determine the association of physical activity and sedentary behaviour with fatigue and HRQoL in cancer survivors.

Currently, randomized controlled trials (RCTs) report low to moderate effect sizes regarding the effects of physical activity on fatigue and HRQoL. Possibly, this is caused by differences in several components of exercise, including exercise frequency, intensity, time and type (often referred to as the FITT factors), and the mode and timing of the intervention delivery. To further optimize physical activity interventions, more insight in the optimal intervention related characteristics and the mechanisms of physical activity underlying the effects on fatigue and HRQoL is necessary. Mechanisms possibly involved in the effects of physical activity on fatigue and HRQoL are changes in muscular, immunological and insulin-related variables. Possibly, exercise may exert its effect on fatigue by reducing inflammation, reducing the level of IGF and/or by increasing muscle mass and strength.

Finally, more insight in how patients perceive potential effects of exercise on their HRQoL could increase knowledge on mechanisms involved in the effect of exercise interventions on HRQoL. Possibly, there are other variables that mediate the effects of physical fitness on QoL which are not yet investigated.