This is a clinical practice guideline for cancer patients currently undergoing chemotherapy and/or radiotherapy. The guideline examines exercise treatment during active cancer treatment, with the “active treatment” period defined as the period from diagnosis until either 3 weeks post-surgery or one week after the last radiotherapy, or from diagnosis until 3 weeks after the last chemotherapy cycle. Exercise treatment includes any exercise program in any setting. Outcomes of interest included quality of life, cardiopulmonary function, fatigue, and safety of exercise treatments (i.e. frequency and type of adverse events).