Active Surveillance is the watchful waiting of a patients’ condition by a doctor. Surveillance is carried out instead of active treatment when the risks of the treatment outweigh the benefiits. For example the risk of some small, non aggressive, localised prostate cancers ever spreading is very low, however the treatment to remove can leave the patient with urinary symptoms and other side effects. In this case the cancer is closely monitored to make sure it does not spread. If it does spread active treatment will be carried out.