The concept of active surveillance applies to certain patients who are not required to have surgery immediately and who are recommended to wait. Some patients who suffer from prostate cancer are sometimes advised not to do any radical surgical procedures, as their cancer is not life threatening. Additionally, this technique is also applied when elderly people are diagnosed with certain types of less severe cancer, where surgery or other treatments might endanger the patient's life more than cancer itself. During active surveillance, the patient's cancer is monitored carefully and they are required to undergo periodical tests so that their doctor can observe any significant changes.