Physical activity is not only efficient for primary prevention of several cancer types, but it also plays an important role in cancer survivors. Physical activity after a cancer diagnosis has been associated with reduced overall and cancer-specific mortality. It has significant positive effects on physical fitness and several cancer-related symptoms including fatigue, sleep disturbance, depression and anxiety. The evidence is considerable and consistent for breast, colorectal and endometrial cancers. However, patients are generally insufficiently active, and participation rates in physical activity opportunities offered by specialized organizations are low. This pilot study will evaluate the feasibility, efficacy and cost-effectiveness of an intervention seeking to increase active lifestyle and physical activity participation of cancer patients. To encourage this behavioural change, motivational interviewing will be used, a patient-centred approach aimed at increasing the patients' motivation for a behavioural change through open-ended discussions.