Design. The purpose of this review is the analysis of the literature concerning the effects of physical exercise in cancer patients undergoing medical oncologic treatment. Papers were retrieved from the scrutiny of 15 reviews/meta-analyses published in the last 2 years, which, however, pooled different populations of patients (surgical and medical patients, receiving or not an oncologic therapy, harboring a cancer, or being survivors). Results. We reviewed the data of 35 RCTs on the use of physical exercise in cancer patients, distinguishing well-nourished from malnourished patients. The conclusions of our study are the following: No major difference between well-nourished and malnourished patients as regards compliance/adherence with physical exercise and outcomes. Compliance with physical exercise was reported in about 70% of the studies. Compared with a control group receiving the usual care, in patients who practiced physical exercise, a benefit in some parameters of physical function and quality of life and lean body mass (LBM) was reported in 61%, 47%, and 12%, respectively, of the studies in non-malnourished patients, and in 50%, 100%, and 36%, respectively, of the studies in malnourished patients. The benefit in LBM was more frequently reported in weight-losing patients. There was no strict association among the results of different outcomes (muscle function vs. quality of life vs. LBM). There are still some ill-defined issues, including the optimal physical regimen (with some authors favoring high-intensity interval training and resistance) and the place of exercising (patients usually preferring home exercises, which, however, have been proved less efficacious).